diff --git a/examples/parameter_example.yml b/examples/parameter_example.yml
index 996e35e41a3a6090a11ecf30a9decb391865ed63..6aeeaad3e41498b48e215f0a761ecdffb486a118 100644
--- a/examples/parameter_example.yml
+++ b/examples/parameter_example.yml
@@ -338,6 +338,11 @@ EAGLEChemistry:
 
 # Parameters related to star formation models  -----------------------------------------------
 
+# GEAR star formation model (Revaz and Jablonka 2018)
+GEARStarFormation:
+  star_formation_efficiency: 0.01   # star formation efficiency (c_*)
+  maximal_temperature:  3e4         # Upper limit to the temperature of a star forming particle
+
 # EAGLE star formation model (Schaye and Dalla Vecchia 2008)
 EAGLEStarFormation:
   EOS_density_norm_H_p_cm3:          0.1       # Physical density used for the normalisation of the EOS assumed for the star-forming gas in Hydrogen atoms per cm^3.
diff --git a/src/cell.c b/src/cell.c
index f4903f024b10c7cc7867291b597a3bdf42997c27..0649d31b38279f3a75ec2b439f71de105425ae27 100644
--- a/src/cell.c
+++ b/src/cell.c
@@ -4413,7 +4413,7 @@ void cell_drift_part(struct cell *c, const struct engine *e, int force) {
       if (part_is_active(p, e)) {
         hydro_init_part(p, &e->s->hs);
         chemistry_init_part(p, e->chemistry);
-        star_formation_init_part(p, e->star_formation);
+        star_formation_init_part(p, xp, e->star_formation);
         tracers_after_init(p, xp, e->internal_units, e->physical_constants,
                            with_cosmology, e->cosmology, e->hydro_properties,
                            e->cooling_func, e->time);
diff --git a/src/collectgroup.c b/src/collectgroup.c
index d17608d67a291ae412728b3fcd9ea80c192802bf..8dd9e974f41c979f4c50e84fb555f9b80db19e25 100644
--- a/src/collectgroup.c
+++ b/src/collectgroup.c
@@ -122,7 +122,8 @@ void collectgroup1_apply(const struct collectgroup1 *grp1, struct engine *e) {
   e->total_nr_cells = grp1->total_nr_cells;
   e->total_nr_tasks = grp1->total_nr_tasks;
   e->tasks_per_cell_max = grp1->tasks_per_cell_max;
-  e->sfh = grp1->sfh;
+
+  star_formation_logger_add_to_accumulator(&e->sfh, &grp1->sfh);
 }
 
 /**
diff --git a/src/cooling/grackle/cooling.h b/src/cooling/grackle/cooling.h
index 1abbe5d3827726bde34502cd2b6a1d18cd309950..57f4b146c451557365e08d260ddd45276844af9c 100644
--- a/src/cooling/grackle/cooling.h
+++ b/src/cooling/grackle/cooling.h
@@ -697,6 +697,17 @@ __attribute__((always_inline)) INLINE static void cooling_cool_part(
   xp->cooling_data.radiated_energy -= hydro_get_mass(p) * cooling_du_dt * dt;
 }
 
+/**
+ * @brief Compute the temperature of a #part based on the cooling function.
+ *
+ * @param phys_const #phys_const data structure.
+ * @param hydro_props The properties of the hydro scheme.
+ * @param us The internal system of units.
+ * @param cosmo #cosmology data structure.
+ * @param cooling #cooling_function_data struct.
+ * @param p #part data.
+ * @param xp Pointer to the #xpart data.
+ */
 static INLINE float cooling_get_temperature(
     const struct phys_const* restrict phys_const,
     const struct hydro_props* restrict hydro_props,
@@ -704,9 +715,30 @@ static INLINE float cooling_get_temperature(
     const struct cosmology* restrict cosmo,
     const struct cooling_function_data* restrict cooling,
     const struct part* restrict p, const struct xpart* restrict xp) {
+  // TODO use the grackle library
+
+  /* Physical constants */
+  const double m_H = phys_const->const_proton_mass;
+  const double k_B = phys_const->const_boltzmann_k;
 
-  error("This function needs implementing!!");
-  return 0.;
+  /* Gas properties */
+  const double T_transition = hydro_props->hydrogen_ionization_temperature;
+  const double mu_neutral = hydro_props->mu_neutral;
+  const double mu_ionised = hydro_props->mu_ionised;
+
+  /* Particle temperature */
+  const double u = hydro_get_physical_internal_energy(p, xp, cosmo);
+
+  /* Temperature over mean molecular weight */
+  const double T_over_mu = hydro_gamma_minus_one * u * m_H / k_B;
+
+  /* Are we above or below the HII -> HI transition? */
+  if (T_over_mu > (T_transition + 1.) / mu_ionised)
+    return T_over_mu * mu_ionised;
+  else if (T_over_mu < (T_transition - 1.) / mu_neutral)
+    return T_over_mu * mu_neutral;
+  else
+    return T_transition;
 }
 
 /**
diff --git a/src/engine.c b/src/engine.c
index 8f14cfd0088cff9d47bee38662a5aeff357dd8e0..33f94e9c16475b5281cdb5948e6b31e1026c7d46 100644
--- a/src/engine.c
+++ b/src/engine.c
@@ -5062,6 +5062,11 @@ void engine_init(struct engine *e, struct space *s, struct swift_params *params,
         parser_get_opt_param_double(params, "FOF:delta_time", -1.);
   }
 
+  /* Initialize the star formation history structure */
+  if (e->policy & engine_policy_star_formation) {
+    star_formation_logger_accumulator_init(&e->sfh);
+  }
+
   engine_init_output_lists(e, params);
 }
 
diff --git a/src/engine.h b/src/engine.h
index 8296933561b5f7664904d439ec6ca20f1e37a4b8..967a430871648ac4cb91f390f8b85675a314d3a8 100644
--- a/src/engine.h
+++ b/src/engine.h
@@ -237,7 +237,7 @@ struct engine {
   long long b_updates_since_rebuild;
 
   /* Star formation logger information */
-  struct star_formation_history sfh;
+  struct star_formation_history_accumulator sfh;
 
   /* Properties of the previous step */
   int step_props;
diff --git a/src/hydro/Gadget2/hydro_part.h b/src/hydro/Gadget2/hydro_part.h
index 7a8844d560561dae80c676a0b5bb72b34416d080..853d2adf17bc069434562fa96ddb881f760f6830 100644
--- a/src/hydro/Gadget2/hydro_part.h
+++ b/src/hydro/Gadget2/hydro_part.h
@@ -155,6 +155,9 @@ struct part {
   /*! Black holes information (e.g. swallowing ID) */
   struct black_holes_part_data black_holes_data;
 
+  /* Additional data used by the star formation */
+  struct star_formation_part_data sf_data;
+
   /* Time-step length */
   timebin_t time_bin;
 
diff --git a/src/runner.c b/src/runner.c
index 7320fd8744948632cd6a08b2434768b47d837360..644d7f6171887a3a44395767353c1de84aa513d9 100644
--- a/src/runner.c
+++ b/src/runner.c
@@ -2272,7 +2272,7 @@ void runner_do_ghost(struct runner *r, struct cell *c, int timer) {
             /* Re-initialise everything */
             hydro_init_part(p, hs);
             chemistry_init_part(p, chemistry);
-            star_formation_init_part(p, star_formation);
+            star_formation_init_part(p, xp, star_formation);
             tracers_after_init(p, xp, e->internal_units, e->physical_constants,
                                with_cosmology, e->cosmology,
                                e->hydro_properties, e->cooling_func, e->time);
diff --git a/src/runner_doiact.h b/src/runner_doiact.h
index 6caa287cf726f85778ef5abdc184acaf759e8b0e..1a39c8d49f2c4234c04982e255705f06ec1c5d38 100644
--- a/src/runner_doiact.h
+++ b/src/runner_doiact.h
@@ -884,7 +884,6 @@ void DOSELF_SUBSET(struct runner *r, struct cell *restrict ci,
 
   const int count_i = ci->hydro.count;
   struct part *restrict parts_j = ci->hydro.parts;
-
   /* Loop over the parts in ci. */
   for (int pid = 0; pid < count; pid++) {
 
diff --git a/src/space.c b/src/space.c
index 49c714743728a3b93f631434d87de69a61dd716f..250af5efafa506408c9fd91c1adffb7cd96a1a21 100644
--- a/src/space.c
+++ b/src/space.c
@@ -4365,7 +4365,7 @@ void space_init_parts_mapper(void *restrict map_data, int count,
   for (int k = 0; k < count; k++) {
     hydro_init_part(&parts[k], hs);
     chemistry_init_part(&parts[k], e->chemistry);
-    star_formation_init_part(&parts[k], e->star_formation);
+    star_formation_init_part(&parts[k], &xparts[k], e->star_formation);
     tracers_after_init(&parts[k], &xparts[k], e->internal_units,
                        e->physical_constants, with_cosmology, e->cosmology,
                        e->hydro_properties, e->cooling_func, e->time);
diff --git a/src/star_formation.c b/src/star_formation.c
index 698a64cc636dd79f00feac3f6cc88bf519fe09c1..60cff1e2e68feaf7e71705b5079294ec478fad42 100644
--- a/src/star_formation.c
+++ b/src/star_formation.c
@@ -24,6 +24,7 @@
 #include "part.h"
 #include "restart.h"
 #include "star_formation.h"
+#include "star_formation_io.h"
 #include "units.h"
 
 /**
diff --git a/src/star_formation/EAGLE/star_formation.h b/src/star_formation/EAGLE/star_formation.h
index 694cac1512d91ef3d640185cbf9b614773263a75..f2c77e036842b4ca040c58a6bcad1513b03a42bd 100644
--- a/src/star_formation/EAGLE/star_formation.h
+++ b/src/star_formation/EAGLE/star_formation.h
@@ -691,6 +691,7 @@ star_formation_first_init_part(const struct phys_const* restrict phys_const,
  * @param data The global star_formation information.
  */
 __attribute__((always_inline)) INLINE static void star_formation_init_part(
-    struct part* restrict p, const struct star_formation* data) {}
+    struct part* restrict p, struct xpart* restrict xp,
+    const struct star_formation* data) {}
 
 #endif /* SWIFT_EAGLE_STAR_FORMATION_H */
diff --git a/src/star_formation/EAGLE/star_formation_logger.h b/src/star_formation/EAGLE/star_formation_logger.h
index d634c876e52d45588ed0b93c0afc09731317c037..a843f63ce518aa9be6b1d389d42cf71c8608b903 100644
--- a/src/star_formation/EAGLE/star_formation_logger.h
+++ b/src/star_formation/EAGLE/star_formation_logger.h
@@ -87,6 +87,28 @@ INLINE static void star_formation_logger_add(
   sf_update->SFR_inactive += sf_add->SFR_inactive;
 }
 
+/**
+ * @brief add a star formation history struct to the engine star formation
+ * history accumulator struct
+ *
+ * @param sf_add the star formation accumulator struct which we want to add to
+ * the star formation history
+ * @param sf_update the star formation structure which we want to update
+ */
+INLINE static void star_formation_logger_add_to_accumulator(
+    struct star_formation_history_accumulator *sf_update,
+    const struct star_formation_history *sf_add) {
+
+  /* Update the SFH structure */
+  sf_update->new_stellar_mass += sf_add->new_stellar_mass;
+
+  sf_update->SFR_active += sf_add->SFR_active;
+
+  sf_update->SFRdt_active += sf_add->SFRdt_active;
+
+  sf_update->SFR_inactive += sf_add->SFR_inactive;
+}
+
 /**
  * @brief Initialize the star formation history structure in the #engine
  *
@@ -105,6 +127,24 @@ INLINE static void star_formation_logger_init(
   sfh->SFR_inactive = 0.f;
 }
 
+/**
+ * @brief Initialize the star formation history structure in the #engine
+ *
+ * @param sfh The pointer to the star formation history structure
+ */
+INLINE static void star_formation_logger_accumulator_init(
+    struct star_formation_history_accumulator *sfh) {
+
+  /* Initialize the collecting SFH structure to zero */
+  sfh->new_stellar_mass = 0.f;
+
+  sfh->SFR_active = 0.f;
+
+  sfh->SFRdt_active = 0.f;
+
+  sfh->SFR_inactive = 0.f;
+}
+
 /**
  * @brief Write the final SFH to a file
  *
@@ -117,7 +157,7 @@ INLINE static void star_formation_logger_init(
  */
 INLINE static void star_formation_logger_write_to_log_file(
     FILE *fp, const double time, const double a, const double z,
-    const struct star_formation_history sf, const int step) {
+    const struct star_formation_history_accumulator sf, const int step) {
 
   /* Calculate the total SFR */
   const float totalSFR = sf.SFR_active + sf.SFR_inactive;
diff --git a/src/star_formation/EAGLE/star_formation_logger_struct.h b/src/star_formation/EAGLE/star_formation_logger_struct.h
index 2a23659c4d931735d1b82a6143b3d9f871f7137a..c03a00c97ead46f552350a43574c5bbe7ac6df1b 100644
--- a/src/star_formation/EAGLE/star_formation_logger_struct.h
+++ b/src/star_formation/EAGLE/star_formation_logger_struct.h
@@ -34,4 +34,21 @@ struct star_formation_history {
   float SFRdt_active;
 };
 
+/* Starformation history struct for the engine.
+ Allows to integrate in time some values.
+ Nothing to do in EAGLE => copy of star_formation_history */
+struct star_formation_history_accumulator {
+  /*! Total new stellar mass */
+  float new_stellar_mass;
+
+  /*! SFR of all particles */
+  float SFR_inactive;
+
+  /*! SFR of active particles */
+  float SFR_active;
+
+  /*! SFR*dt of active particles */
+  float SFRdt_active;
+};
+
 #endif /* SWIFT_EAGLE_STAR_FORMATION_LOGGER_STRUCT_H */
diff --git a/src/star_formation/EAGLE/star_formation_struct.h b/src/star_formation/EAGLE/star_formation_struct.h
index 41247e160a3eddbc9184c59b67cfa2a1d7259a05..8caac49d4b57652c5db9ae93e3789dc690e6d23f 100644
--- a/src/star_formation/EAGLE/star_formation_struct.h
+++ b/src/star_formation/EAGLE/star_formation_struct.h
@@ -29,4 +29,6 @@ struct star_formation_xpart_data {
   float SFR;
 };
 
+struct star_formation_part_data {};
+
 #endif /* SWIFT_EAGLE_STAR_FORMATION_STRUCT_H */
diff --git a/src/star_formation/GEAR/star_formation.h b/src/star_formation/GEAR/star_formation.h
index c479feb5c66328f9fab8bf62593ca66b6658b79e..ac423a51865609460e870f65b1eeeb266182e2ef 100644
--- a/src/star_formation/GEAR/star_formation.h
+++ b/src/star_formation/GEAR/star_formation.h
@@ -1,6 +1,7 @@
 /*******************************************************************************
  * This file is part of SWIFT.
- * Copyright (c) 2018 Folkert Nobels (nobels@strw.leidenuniv.nl)
+ * Coypright (c) 2019 Loic Hausammann (loic.hausammann@epfl.ch)
+ *               2019 Fabien Jeanquartier (fabien.jeanquartier@epfl.ch)
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published
@@ -20,20 +21,24 @@
 #define SWIFT_GEAR_STAR_FORMATION_H
 
 /* Local includes */
+#include "cooling.h"
 #include "cosmology.h"
+#include "engine.h"
 #include "entropy_floor.h"
 #include "error.h"
 #include "hydro_properties.h"
 #include "parser.h"
 #include "part.h"
 #include "physical_constants.h"
+#include "random.h"
+#include "star_formation_struct.h"
 #include "units.h"
 
 /**
  * @brief Calculate if the gas has the potential of becoming
  * a star.
  *
- * No star formation should occur, so return 0.
+ * Use the star formation criterion given by eq. 3 in Revaz & Jablonka 2018.
  *
  * @param starform the star formation law properties to use.
  * @param p the gas particles.
@@ -46,7 +51,7 @@
  *
  */
 INLINE static int star_formation_is_star_forming(
-    const struct part* restrict p, const struct xpart* restrict xp,
+    struct part* restrict p, struct xpart* restrict xp,
     const struct star_formation* starform, const struct phys_const* phys_const,
     const struct cosmology* cosmo,
     const struct hydro_props* restrict hydro_props,
@@ -54,14 +59,43 @@ INLINE static int star_formation_is_star_forming(
     const struct cooling_function_data* restrict cooling,
     const struct entropy_floor_properties* restrict entropy_floor) {
 
-  return 0;
+  const float temperature = cooling_get_temperature(phys_const, hydro_props, us,
+                                                    cosmo, cooling, p, xp);
+
+  const float temperature_max = starform->maximal_temperature;
+
+  /* Check the temperature criterion */
+  if (temperature > temperature_max) {
+    return 0;
+  }
+
+  /* Get the required variables */
+  const float sigma2 = p->sf_data.sigma2;
+  const float n_jeans_2_3 = starform->n_jeans_2_3;
+
+  const float h = p->h;
+  const float density = hydro_get_physical_density(p, cosmo);
+
+  // TODO use GRACKLE */
+  const float mu = hydro_props->mu_neutral;
+
+  /* Compute the density criterion */
+  const float coef =
+      M_PI_4 / (phys_const->const_newton_G * n_jeans_2_3 * h * h);
+  const float density_criterion =
+      coef * (hydro_gamma * phys_const->const_boltzmann_k * temperature /
+                  (mu * phys_const->const_proton_mass) +
+              sigma2);
+
+  /* Check the density criterion */
+  return density > density_criterion;
 }
 
 /**
- * @brief Compute the star-formation rate of a given particle and store
- * it into the #xpart.
+ * @brief Compute the star-formation rate of a given particle.
  *
- * Nothing to do here.
+ * Nothing to do here. Everything is done in
+ * #star_formation_should_convert_to_star.
  *
  * @param p #part.
  * @param xp the #xpart.
@@ -71,15 +105,15 @@ INLINE static int star_formation_is_star_forming(
  * @param dt_star The time-step of this particle.
  */
 INLINE static void star_formation_compute_SFR(
-    const struct part* restrict p, struct xpart* restrict xp,
+    struct part* restrict p, struct xpart* restrict xp,
     const struct star_formation* starform, const struct phys_const* phys_const,
     const struct cosmology* cosmo, const double dt_star) {}
 
 /**
  * @brief Decides whether a particle should be converted into a
  * star or not.
- *
- * No SF should occur, so return 0.
+
+ * Compute the star formation rate from eq. 4 in Revaz & Jablonka 2012.
  *
  * @param p The #part.
  * @param xp The #xpart.
@@ -89,18 +123,38 @@ INLINE static void star_formation_compute_SFR(
  * @return 1 if a conversion should be done, 0 otherwise.
  */
 INLINE static int star_formation_should_convert_to_star(
-    const struct part* p, const struct xpart* xp,
-    const struct star_formation* starform, const struct engine* e,
-    const double dt_star) {
+    struct part* p, struct xpart* xp, const struct star_formation* starform,
+    const struct engine* e, const double dt_star) {
+
+  const struct phys_const* phys_const = e->physical_constants;
+  const struct cosmology* cosmo = e->cosmology;
+
+  /* Check that we are running a full time step */
+  if (dt_star == 0.) {
+    return 0;
+  }
+
+  /* Get a few variables */
+  const float G = phys_const->const_newton_G;
+  const float density = hydro_get_physical_density(p, cosmo);
+
+  /* Compute the probability */
+  const float inv_free_fall_time =
+      sqrtf(density * 32.f * G * 0.33333333f * M_1_PI);
+  const float prob = 1.f - exp(-starform->star_formation_efficiency *
+                               inv_free_fall_time * dt_star);
+
+  /* Roll the dice... */
+  const float random_number =
+      random_unit_interval(p->id, e->ti_current, random_number_star_formation);
 
-  return 0;
+  /* Can we form a star? */
+  return random_number < prob;
 }
 
 /**
  * @brief Update the SF properties of a particle that is not star forming.
  *
- * Nothing to do here.
- *
  * @param p The #part.
  * @param xp The #xpart.
  * @param e The #engine.
@@ -115,8 +169,6 @@ INLINE static void star_formation_update_part_not_SFR(
  * @brief Copies the properties of the gas particle over to the
  * star particle.
  *
- * Nothing to do here.
- *
  * @param e The #engine
  * @param p the gas particles.
  * @param xp the additional properties of the gas particles.
@@ -133,21 +185,33 @@ INLINE static void star_formation_copy_properties(
     const struct phys_const* phys_const,
     const struct hydro_props* restrict hydro_props,
     const struct unit_system* restrict us,
-    const struct cooling_function_data* restrict cooling) {}
+    const struct cooling_function_data* restrict cooling) {
 
-/**
- * @brief initialization of the star formation law
- *
- * @param parameter_file The parsed parameter file
- * @param phys_const Physical constants in internal units
- * @param us The current internal system of units
- * @param starform the star formation law properties to initialize
- *
- */
-INLINE static void starformation_init_backend(
-    struct swift_params* parameter_file, const struct phys_const* phys_const,
-    const struct unit_system* us, const struct hydro_props* hydro_props,
-    const struct star_formation* starform) {}
+  /* Store the current mass */
+  sp->mass = hydro_get_mass(p);
+  sp->birth.mass = sp->mass;
+
+  /* Store either the birth_scale_factor or birth_time depending  */
+  if (with_cosmology) {
+    sp->birth_scale_factor = cosmo->a;
+  } else {
+    sp->birth_time = e->time;
+  }
+
+  // TODO copy only metals
+  /* Store the chemistry struct in the star particle */
+  sp->chemistry_data = p->chemistry_data;
+
+  /* Store the tracers data */
+  sp->tracers_data = xp->tracers_data;
+
+  /* Store the birth density in the star particle */
+  sp->birth.density = hydro_get_physical_density(p, cosmo);
+
+  /* Store the birth temperature*/
+  sp->birth.temperature = cooling_get_temperature(phys_const, hydro_props, us,
+                                                  cosmo, cooling, p, xp);
+}
 
 /**
  * @brief Prints the used parameters of the star formation law
@@ -156,7 +220,6 @@ INLINE static void starformation_init_backend(
  */
 INLINE static void starformation_print_backend(
     const struct star_formation* starform) {
-
   message("Star formation law is 'GEAR'");
 }
 
@@ -164,12 +227,22 @@ INLINE static void starformation_print_backend(
  * @brief Finishes the density calculation.
  *
  * @param p The particle to act upon
- * @param cd The global star_formation information.
+ * @param xp The extended particle data to act upon
+ * @param sf The global star_formation information.
  * @param cosmo The current cosmological model.
  */
 __attribute__((always_inline)) INLINE static void star_formation_end_density(
-    struct part* restrict p, const struct star_formation* cd,
-    const struct cosmology* cosmo) {}
+    struct part* restrict p, const struct star_formation* sf,
+    const struct cosmology* cosmo) {
+
+  // TODO move into pressure floor
+  /* To finish the turbulence estimation we devide by the density */
+  p->sf_data.sigma2 /=
+      pow_dimension(p->h) * hydro_get_physical_density(p, cosmo);
+
+  /* Add the cosmological factor */
+  p->sf_data.sigma2 *= cosmo->a * cosmo->a;
+}
 
 /**
  * @brief Sets all particle fields to sensible values when the #part has 0 ngbs.
@@ -183,39 +256,46 @@ __attribute__((always_inline)) INLINE static void
 star_formation_part_has_no_neighbours(struct part* restrict p,
                                       struct xpart* restrict xp,
                                       const struct star_formation* cd,
-                                      const struct cosmology* cosmo) {}
+                                      const struct cosmology* cosmo) {
+
+  // TODO move into pressure floor
+  /* If part has 0 neighbours, the estimation of turbulence is 0 */
+  p->sf_data.sigma2 = 0.f;
+}
 
 /**
  * @brief Sets the star_formation properties of the (x-)particles to a valid
  * start state.
  *
- * Nothing to do here.
- *
+ * @param p Pointer to the particle data.
+ * @param xp Pointer to extended particle data
+ * @param data The global star_formation information.
+ */
+__attribute__((always_inline)) INLINE static void star_formation_init_part(
+    struct part* restrict p, struct xpart* restrict xp,
+    const struct star_formation* data) {
+  p->sf_data.sigma2 = 0.f;
+}
+
+/**
+ * @brief Sets the star_formation properties of the (x-)particles to a valid
+ * start state.
  * @param phys_const The physical constant in internal units.
  * @param us The unit system.
  * @param cosmo The current cosmological model.
  * @param data The global star_formation information used for this run.
  * @param p Pointer to the particle data.
- * @param xp Pointer to the extended particle data.
  */
 __attribute__((always_inline)) INLINE static void
 star_formation_first_init_part(const struct phys_const* restrict phys_const,
                                const struct unit_system* restrict us,
                                const struct cosmology* restrict cosmo,
                                const struct star_formation* data,
-                               const struct part* restrict p,
-                               struct xpart* restrict xp) {}
+                               struct part* restrict p,
+                               struct xpart* restrict xp) {
 
-/**
- * @brief Sets the star_formation properties of the (x-)particles to a valid
- * start state.
- *
- * Nothing to do here.
- *
- * @param p Pointer to the particle data.
- * @param data The global star_formation information.
- */
-__attribute__((always_inline)) INLINE static void star_formation_init_part(
-    struct part* restrict p, const struct star_formation* data) {}
+  /* Nothing special here */
+  star_formation_init_part(p, xp, data);
+}
 
 #endif /* SWIFT_GEAR_STAR_FORMATION_H */
diff --git a/src/star_formation/GEAR/star_formation_iact.h b/src/star_formation/GEAR/star_formation_iact.h
index 749b608068650a27cbe4c9a0ca4126d2740337f3..7325b92af2840b317cf1a924a1e509b34bdffba3 100644
--- a/src/star_formation/GEAR/star_formation_iact.h
+++ b/src/star_formation/GEAR/star_formation_iact.h
@@ -1,6 +1,7 @@
 /*******************************************************************************
  * This file is part of SWIFT.
- * Copyright (c) 2019 Loic Hausammann (loic.hausammann@epfl.ch)
+ * Coypright (c) 2019 Loic Hausammann (loic.hausammann@epfl.ch)
+ *               2019 Fabien Jeanquartier (fabien.jeanquartier@epfl.ch)
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published
@@ -28,6 +29,8 @@
  * @brief do star_formation computation after the runner_iact_density (symmetric
  * version)
  *
+ * Compute the velocity dispersion follow eq. 2 in Revaz & Jablonka 2018.
+ *
  * @param r2 Comoving square distance between the two particles.
  * @param dx Comoving vector separating both particles (pi - pj).
  * @param hi Comoving smoothing-length of particle i.
@@ -39,7 +42,28 @@
  */
 __attribute__((always_inline)) INLINE static void runner_iact_star_formation(
     float r2, const float *dx, float hi, float hj, struct part *restrict pi,
-    struct part *restrict pj, float a, float H) {}
+    struct part *restrict pj, float a, float H) {
+
+  float wi;
+  float wj;
+  /* Evaluation of the SPH kernel */
+  kernel_eval(sqrt(r2) / hi, &wi);
+  kernel_eval(sqrt(r2) / hj, &wj);
+
+  /* Delta v */
+  float dv[3] = {pi->v[0] - pj->v[0], pi->v[1] - pj->v[1], pi->v[2] - pj->v[2]};
+
+  /* Norms at power 2 */
+  const float norm_v2 = dv[0] * dv[0] + dv[1] * dv[1] + dv[2] * dv[2];
+  const float norm_x2 = dx[0] * dx[0] + dx[1] * dx[1] + dx[2] * dx[2];
+
+  /* Compute the velocity dispersion */
+  const float sigma2 = norm_v2 + H * norm_x2;
+
+  /* Compute the velocity dispersion */
+  pi->sf_data.sigma2 += sigma2 * wi * hydro_get_mass(pj);
+  pj->sf_data.sigma2 += sigma2 * wj * hydro_get_mass(pi);
+}
 
 /**
  * @brief do star_formation computation after the runner_iact_density (non
@@ -58,6 +82,23 @@ __attribute__((always_inline)) INLINE static void
 runner_iact_nonsym_star_formation(float r2, const float *dx, float hi, float hj,
                                   struct part *restrict pi,
                                   const struct part *restrict pj, float a,
-                                  float H) {}
+                                  float H) {
+  float wi;
+  /* Evaluation of the SPH kernel */
+  kernel_eval(sqrt(r2) / hi, &wi);
+
+  /* Delta v */
+  float dv[3] = {pi->v[0] - pj->v[0], pi->v[1] - pj->v[1], pi->v[2] - pj->v[2]};
+
+  /* Norms at power 2 */
+  const float norm_v2 = dv[0] * dv[0] + dv[1] * dv[1] + dv[2] * dv[2];
+  const float norm_x2 = dx[0] * dx[0] + dx[1] * dx[1] + dx[2] * dx[2];
+
+  /* Compute the velocity dispersion */
+  const float sigma2 = norm_v2 + H * norm_x2;
+
+  /* Compute the velocity dispersion */
+  pi->sf_data.sigma2 += sigma2 * wi * hydro_get_mass(pj);
+}
 
 #endif /* SWIFT_GEAR_STAR_FORMATION_IACT_H */
diff --git a/src/star_formation/GEAR/star_formation_io.h b/src/star_formation/GEAR/star_formation_io.h
index 6ef04c49c4abcd00175aaa164271628a9ff89360..3e021f7844c1deaeca40d7144d6f7b69cb6c2bdb 100644
--- a/src/star_formation/GEAR/star_formation_io.h
+++ b/src/star_formation/GEAR/star_formation_io.h
@@ -1,6 +1,7 @@
 /*******************************************************************************
  * This file is part of SWIFT.
- * Copyright (c) 2018 Folkert Nobels (nobels@strw.leidenuniv.nl)
+ * Coypright (c) 2019 Loic Hausammann (loic.hausammann@epfl.ch)
+ *               2019 Fabien Jeanquartier (fabien.jeanquartier@epfl.ch)
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published
@@ -37,8 +38,40 @@
 __attribute__((always_inline)) INLINE static int star_formation_write_particles(
     const struct part* parts, const struct xpart* xparts,
     struct io_props* list) {
-
+  /* Nothing to write here */
   return 0;
 }
 
+/**
+ * @brief initialization of the star formation law
+ *
+ * @param parameter_file The parsed parameter file
+ * @param phys_const Physical constants in internal units
+ * @param us The current internal system of units
+ * @param starform the star formation law properties to initialize
+ *
+ */
+INLINE static void starformation_init_backend(
+    struct swift_params* parameter_file, const struct phys_const* phys_const,
+    const struct unit_system* us, const struct hydro_props* hydro_props,
+    struct star_formation* starform) {
+
+  // TODO move into pressure floor
+  starform->n_jeans_2_3 =
+      parser_get_param_float(parameter_file, "GEARStarFormation:NJeans");
+  starform->n_jeans_2_3 = pow(starform->n_jeans_2_3, 2. / 3.);
+
+  /* Star formation efficiency */
+  starform->star_formation_efficiency = parser_get_param_double(
+      parameter_file, "GEARStarFormation:star_formation_efficiency");
+
+  /* Maximum temperature for star formation */
+  starform->maximal_temperature = parser_get_param_double(
+      parameter_file, "GEARStarFormation:maximal_temperature");
+
+  /* Apply unit change */
+  starform->maximal_temperature *=
+      units_cgs_conversion_factor(us, UNIT_CONV_TEMPERATURE);
+}
+
 #endif /* SWIFT_STAR_FORMATION_GEAR_IO_H */
diff --git a/src/star_formation/GEAR/star_formation_logger.h b/src/star_formation/GEAR/star_formation_logger.h
index 5b9e033d21d3d202f3c289d1dd6a843ba17fa524..84475909c0f524a4f930a48dbcc3b0943719f8b0 100644
--- a/src/star_formation/GEAR/star_formation_logger.h
+++ b/src/star_formation/GEAR/star_formation_logger.h
@@ -1,6 +1,7 @@
 /*******************************************************************************
  * This file is part of SWIFT.
- * Copyright (c) 2019 Folkert Nobels (nobels@strw.leidenuniv.nl)
+ * Coypright (c) 2019 Loic Hausammann (loic.hausammann@epfl.ch)
+ *               2019 Fabien Jeanquartier (fabien.jeanquartier@epfl.ch)
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published
@@ -27,16 +28,28 @@
 #include "hydro.h"
 #include "part.h"
 #include "star_formation_logger_struct.h"
+#include "units.h"
 
 /**
- * @brief Update the stellar mass in the current cell after creating
- * the new star particle spart sp
+ * @brief Update the stellar quantities in the current cell after creating
+ * the new star particle spart sp.
  *
+ * @param time_step, the current time step of the simulation
  * @param sp new created star particle
  * @param sf the star_formation_history struct of the current cell
  */
 INLINE static void star_formation_logger_log_new_spart(
-    struct spart *sp, struct star_formation_history *sf) {}
+    const struct spart *sp, struct star_formation_history *sf) {
+
+  /* Add mass of created sparticle to the total stellar mass in this cell */
+  sf->new_stellar_mass += sp->mass;
+
+  /* Increase the number of stars */
+  sf->number_new_stars += 1;
+
+  /* No need to deal with the integrated quantities, only the engine's one is
+   * updated */
+}
 
 /**
  * @brief Initialize the star formation history struct in the case the cell is
@@ -45,41 +58,42 @@ INLINE static void star_formation_logger_log_new_spart(
  * @param sf the star_formation_history struct we want to initialize
  */
 INLINE static void star_formation_logger_log_inactive_cell(
-    struct star_formation_history *sf) {}
+    struct star_formation_history *sf) {
 
-/**
- * @brief add a star formation history struct to an other star formation history
- * struct
- *
- * @param sf_add the star formation struct which we want to add to the star
- * formation history
- * @param sf_update the star formation structure which we want to update
- */
-INLINE static void star_formation_logger_add(
-    struct star_formation_history *sf_update,
-    const struct star_formation_history *sf_add) {}
+  /* Initialize the stellar mass to zero */
+  sf->new_stellar_mass = 0.f;
 
+  /* initialize number of stars to zero*/
+  sf->number_new_stars = 0;
+}
 /**
  * @brief Initialize the star formation history structure in the #engine
  *
  * @param sfh The pointer to the star formation history structure
  */
 INLINE static void star_formation_logger_init(
-    struct star_formation_history *sfh) {}
+    struct star_formation_history *sfh) {
+  /* Initialize the collecting SFH structure to zero */
+  sfh->new_stellar_mass = 0.f;
+  sfh->number_new_stars = 0;
+}
 
 /**
- * @brief Write the final SFH to a file
+ * @brief add a star formation history struct to an other star formation history
+ * struct
  *
- * @param fp The file to write to.
- * @param time the simulation time (time since Big Bang) in internal units.
- * @param a the scale factor.
- * @param z the redshift.
- * @param sf the #star_formation_history struct.
- * @param step The time-step of the simulation.
+ * @param sf_add the star formation struct which we want to add to the star
+ * formation history
+ * @param sf_update the star formation structure which we want to update
  */
-INLINE static void star_formation_logger_write_to_log_file(
-    FILE *fp, const double time, const double a, const double z,
-    const struct star_formation_history sf, const int step) {}
+INLINE static void star_formation_logger_add(
+    struct star_formation_history *sf_update,
+    const struct star_formation_history *sf_add) {
+
+  /* Update the SFH structure */
+  sf_update->number_new_stars += sf_add->number_new_stars;
+  sf_update->new_stellar_mass += sf_add->new_stellar_mass;
+}
 
 /**
  * @brief Initialize the SFH logger file
@@ -90,13 +104,47 @@ INLINE static void star_formation_logger_write_to_log_file(
  */
 INLINE static void star_formation_logger_init_log_file(
     FILE *fp, const struct unit_system *restrict us,
-    const struct phys_const *phys_const) {}
+    const struct phys_const *phys_const) {
+
+  /* Write some general text to the logger file */
+  fprintf(fp, "# Star Formation History Logger file\n");
+  fprintf(fp, "######################################################\n");
+  fprintf(fp, "# The quantities are all given in internal physical units!\n");
+  fprintf(fp, "#\n");
+  fprintf(fp, "# (0) Simulation step\n");
+  fprintf(fp,
+          "# (1) Time since Big Bang (cosmological run), Time since start of "
+          "the simulation (non-cosmological run).\n");
+  fprintf(fp, "#     Unit = %e seconds\n", us->UnitTime_in_cgs);
+  fprintf(fp, "#     Unit = %e yr or %e Myr\n", 1.f / phys_const->const_year,
+          1.f / phys_const->const_year / 1e6);
+  fprintf(fp, "# (2) Scale factor (no unit)\n");
+  fprintf(fp, "# (3) Redshift     (no unit)\n");
+  fprintf(fp,
+          "# (4) Total number of stars formed in the simulation (no unit)\n");
+  fprintf(fp, "# (5) Total stellar mass formed in the simulation.\n");
+  fprintf(fp, "#     Unit = %e gram\n", us->UnitMass_in_cgs);
+  fprintf(fp, "#     Unit = %e solar mass\n",
+          1.f / phys_const->const_solar_mass);
+  fprintf(fp,
+          "# (6) Number of stars formed in the current time step (no unit).\n");
+  fprintf(fp, "# (7) Mass of stars formed in the current time step.\n");
+  fprintf(fp, "#     Unit = %e gram\n", us->UnitMass_in_cgs);
+  fprintf(fp, "#     Unit = %e solar mass\n",
+          1.f / phys_const->const_solar_mass);
+  fprintf(fp,
+          "# (0)         (1)            (2)          (3)                   (4) "
+          "      (5)        (6)        (7)\n");
+}
 
 /**
  * @brief Add the SFR tracer to the total active SFR of this cell
  *
+ * Nothing to do here
+ *
  * @param p the #part
  * @param xp the #xpart
+ *
  * @param sf the SFH logger struct
  * @param dt_star The length of the time-step in physical internal units.
  */
@@ -108,6 +156,8 @@ INLINE static void star_formation_logger_log_active_part(
  * @brief Add the SFR tracer to the total inactive SFR of this cell as long as
  * the SFR tracer is larger than 0
  *
+ * Nothing to do here
+ *
  * @param p the #part
  * @param xp the #xpart
  * @param sf the SFH logger struct
@@ -116,4 +166,57 @@ INLINE static void star_formation_logger_log_inactive_part(
     const struct part *p, const struct xpart *xp,
     struct star_formation_history *sf) {}
 
+/**
+ * @brief add a star formation history struct to an other star formation history
+ * struct
+ *
+ * @param sf_add the star formation struct which we want to add to the star
+ * formation history
+ * @param sf_update the star formation structure which we want to update
+ */
+INLINE static void star_formation_logger_add_to_accumulator(
+    struct star_formation_history_accumulator *sf_update,
+    const struct star_formation_history *sf_add) {
+
+  /* Update the SFH structure */
+  sf_update->number_new_stars = sf_add->number_new_stars;
+  sf_update->new_stellar_mass = sf_add->new_stellar_mass;
+  sf_update->total_number_stars += sf_add->number_new_stars;
+  sf_update->total_stellar_mass += sf_add->new_stellar_mass;
+}
+
+/**
+ * @brief Write the final SFH to a file
+ *
+ * @param fp The file to write to.
+ * @param time the simulation time (time since Big Bang) in internal units.
+ * @param a the scale factor.
+ * @param z the redshift.
+ * @param sf the #star_formation_history struct.
+ * @param step The time-step of the simulation.
+ */
+INLINE static void star_formation_logger_write_to_log_file(
+    FILE *fp, const double time, const double a, const double z,
+    struct star_formation_history_accumulator sf, const int step) {
+
+  fprintf(fp, "%6d %16e %12.7f %14e %14ld %14e %14ld %14e\n", step, time, a, z,
+          sf.total_number_stars, sf.total_stellar_mass, sf.number_new_stars,
+          sf.new_stellar_mass);
+}
+
+/**
+ * @brief Initialize the star formation history struct in the #engine when
+ * starting the simulation.
+ *
+ * @param sfh the star_formation_history struct we want to initialize
+ */
+INLINE static void star_formation_logger_accumulator_init(
+    struct star_formation_history_accumulator *sfh) {
+  /* Initialize all values to zero */
+  sfh->new_stellar_mass = 0.f;
+  sfh->number_new_stars = 0;
+  sfh->total_number_stars = 0;
+  sfh->total_stellar_mass = 0.f;
+}
+
 #endif /* SWIFT_GEAR_STARFORMATION_LOGGER_H */
diff --git a/src/star_formation/GEAR/star_formation_logger_struct.h b/src/star_formation/GEAR/star_formation_logger_struct.h
index 04b5dfdc038f7b684cfb1f2079d13eb312624b3f..63e3af06a7cd5af375662a1ba28dc5000a69dc3f 100644
--- a/src/star_formation/GEAR/star_formation_logger_struct.h
+++ b/src/star_formation/GEAR/star_formation_logger_struct.h
@@ -1,6 +1,7 @@
 /*******************************************************************************
  * This file is part of SWIFT.
- * Copyright (c) 2019 Folkert Nobels (nobels@strw.leidenuniv.nl)
+ * Coypright (c) 2019 Loic Hausammann (loic.hausammann@epfl.ch)
+ *               2019 Fabien Jeanquartier (fabien.jeanquartier@epfl.ch)
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published
@@ -19,7 +20,33 @@
 #ifndef SWIFT_GEAR_STAR_FORMATION_LOGGER_STRUCT_H
 #define SWIFT_GEAR_STAR_FORMATION_LOGGER_STRUCT_H
 
-/* Starformation history struct */
-struct star_formation_history {};
+/**
+ * Structure containing the star formation information from the cells.
+ */
+struct star_formation_history {
+  /*! Stellar mass created in the current timestep */
+  float new_stellar_mass;
 
-#endif /* SWIFT_NONE_STAR_FORMATION_STRUCT_H */
+  /*! Number of stars created in this timestep */
+  long int number_new_stars;
+};
+
+/**
+ * Structure containing the global star formation information (including time
+ * integrated variables).
+ */
+struct star_formation_history_accumulator {
+  /*! Total stellar mass from the begining of the simulation */
+  float total_stellar_mass;
+
+  /*! Total number of stars */
+  long int total_number_stars;
+
+  /*! Stellar mass created in the current timestep */
+  float new_stellar_mass;
+
+  /*! Number of stars created in this timestep */
+  long int number_new_stars;
+};
+
+#endif /* SWIFT_GEAR_STAR_FORMATION_LOGGER_STRUCT_H */
diff --git a/src/star_formation/GEAR/star_formation_struct.h b/src/star_formation/GEAR/star_formation_struct.h
index 9b4e216fd2955f29d89dade6ee46c0e1af715cdb..2e9a7548f83ca6ae9bb78ee7bcf4be69a0a31489 100644
--- a/src/star_formation/GEAR/star_formation_struct.h
+++ b/src/star_formation/GEAR/star_formation_struct.h
@@ -25,7 +25,27 @@
  */
 struct star_formation_xpart_data {};
 
-/* Starformation struct */
-struct star_formation {};
+struct star_formation_part_data {
+  // TODO move it to the pressure floor
+  /*! Estimation of local turbulence (squared) */
+  float sigma2;
+};
+
+/**
+ * @brief Global star formation properties
+ */
+struct star_formation {
+
+  // TODO move it to pressure floor
+  /*! Number of particle required to resolved the Jeans criterion (at power 2/3)
+   */
+  float n_jeans_2_3;
+
+  /*! Maximal temperature for forming a star */
+  float maximal_temperature;
+
+  /*! Star formation efficiency */
+  float star_formation_efficiency;
+};
 
 #endif /* SWIFT_GEAR_STAR_FORMATION_STRUCT_H */
diff --git a/src/star_formation/none/star_formation.h b/src/star_formation/none/star_formation.h
index 412bda2cc356729bb9f3e3657689fb5bb7b36d8f..6b83010ec5f8935778af8c9ad21010ff3452fc0e 100644
--- a/src/star_formation/none/star_formation.h
+++ b/src/star_formation/none/star_formation.h
@@ -220,6 +220,7 @@ star_formation_first_init_part(const struct phys_const* restrict phys_const,
  * @param data The global star_formation information.
  */
 __attribute__((always_inline)) INLINE static void star_formation_init_part(
-    struct part* restrict p, const struct star_formation* data) {}
+    struct part* restrict p, struct xpart* restrict xp,
+    const struct star_formation* data) {}
 
 #endif /* SWIFT_NONE_STAR_FORMATION_H */
diff --git a/src/star_formation/none/star_formation_logger.h b/src/star_formation/none/star_formation_logger.h
index b4e6987c03d295348fc8c22d66cb20d10e54378c..552df0c6cae533d1eb2678cb23dd675e0a058715 100644
--- a/src/star_formation/none/star_formation_logger.h
+++ b/src/star_formation/none/star_formation_logger.h
@@ -59,6 +59,18 @@ INLINE static void star_formation_logger_add(
     struct star_formation_history *sf_update,
     const struct star_formation_history *sf_add) {}
 
+/**
+ * @brief add a star formation history accumulator struct to an other star
+ * formation history struct
+ *
+ * @param sf_add the star formation accumulator struct which we want to add to
+ * the star formation history
+ * @param sf_update the star formation structure which we want to update
+ */
+INLINE static void star_formation_logger_add_to_accumulator(
+    struct star_formation_history_accumulator *sf_update,
+    const struct star_formation_history *sf_add) {}
+
 /**
  * @brief Initialize the star formation history structure in the #engine
  *
@@ -67,6 +79,14 @@ INLINE static void star_formation_logger_add(
 INLINE static void star_formation_logger_init(
     struct star_formation_history *sfh) {}
 
+/**
+ * @brief Initialize the star formation history structure in the #engine
+ *
+ * @param sfh The pointer to the star formation history structure
+ */
+INLINE static void star_formation_logger_accumulator_init(
+    struct star_formation_history_accumulator *sfh) {}
+
 /**
  * @brief Write the final SFH to a file
  *
@@ -74,12 +94,12 @@ INLINE static void star_formation_logger_init(
  * @param time the simulation time (time since Big Bang) in internal units.
  * @param a the scale factor.
  * @param z the redshift.
- * @param sf the #star_formation_history struct.
+ * @param sf the #star_formation_history_accumulator struct.
  * @param step The time-step of the simulation.
  */
 INLINE static void star_formation_logger_write_to_log_file(
     FILE *fp, const double time, const double a, const double z,
-    const struct star_formation_history sf, const int step) {}
+    const struct star_formation_history_accumulator sf, const int step) {}
 
 /**
  * @brief Initialize the SFH logger file
diff --git a/src/star_formation/none/star_formation_logger_struct.h b/src/star_formation/none/star_formation_logger_struct.h
index 9efda271da96faf2088169fd75d0e3c01247a429..b60c64f2eb47894db828a1bde0ca20803892c7db 100644
--- a/src/star_formation/none/star_formation_logger_struct.h
+++ b/src/star_formation/none/star_formation_logger_struct.h
@@ -22,4 +22,10 @@
 /* Starformation history struct */
 struct star_formation_history {};
 
+/* Starformation history accumulator struct.
+   This structure is only defined in the engine and
+   allows the user to integrate some quantities over time.
+*/
+struct star_formation_history_accumulator {};
+
 #endif /* SWIFT_NONE_STAR_FORMATION_STRUCT_H */
diff --git a/src/star_formation/none/star_formation_struct.h b/src/star_formation/none/star_formation_struct.h
index 27a2adaf83d0a02a0d08e7eef8b45bea630689e4..2f5241a58caf1ca70fa98a40d467c8ff5a3237f7 100644
--- a/src/star_formation/none/star_formation_struct.h
+++ b/src/star_formation/none/star_formation_struct.h
@@ -25,4 +25,10 @@
  */
 struct star_formation_xpart_data {};
 
+/**
+ * @brief Star-formation-related properties stored in the particle
+ * data.
+ */
+struct star_formation_part_data {};
+
 #endif /* SWIFT_NONE_STAR_FORMATION_STRUCT_H */
diff --git a/src/stars.h b/src/stars.h
index dd8390e0206580fc2a07a08e51bb69c6ee5ab5ed..dea6e07a87cabd7d1778ec2a850be4f3b16b04b0 100644
--- a/src/stars.h
+++ b/src/stars.h
@@ -29,6 +29,9 @@
 #elif defined(STARS_EAGLE)
 #include "./stars/EAGLE/stars.h"
 #include "./stars/EAGLE/stars_iact.h"
+#elif defined(STARS_GEAR)
+#include "./stars/GEAR/stars.h"
+#include "./stars/GEAR/stars_iact.h"
 #else
 #error "Invalid choice of star model"
 #endif