diff --git a/callback.c b/callback.c
index 04b4d24..3128135 100644
--- a/callback.c
+++ b/callback.c
@@ -197,17 +197,20 @@ void on_open_STATE (GtkWidget *btt_open_STATE, gpointer user_data) {
           gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("rules"))), //  (GTK_CHECK_BUTTON (btt_open_RULES)),
           gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("data analysis")))); //  (GTK_CHECK_BUTTON (btt_open_DATA)));
 
-  if (! gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("state")))) window_main_child (main_window, STATE);
-}// SWITCH_TO (STATE);}
+  if (! gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("state"))))
+    gtk_window_set_child (main_window, GTK_WIDGET (get_window_child_STATE())); // window_main_child (main_window, STATE);
+}   // SWITCH_TO (STATE);}
 
 void on_open_RULES (GtkWidget *btt_open_RULES, gpointer data) {
   if (0) printf("on_open_RULES   status = %d\n", get_status ());
-  if (! gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("rules")))) window_main_child (main_window, RULES);
+  if (! gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("rules"))))
+        gtk_window_set_child (main_window, GTK_WIDGET (get_window_child_RULES())); // window_main_child (main_window, RULES);
 }// SWITCH_TO (RULES);}
 
 void on_open_DATA  (GtkWidget *btt_open_DATA,  gpointer data) {
   if (0) printf("on_open_DATA    status = %d\n", get_status ());
-  if (! gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("data analysis")))) window_main_child (main_window, DATA);
+  if (! gtk_check_button_get_active (GTK_CHECK_BUTTON (get_GtkButton ("data analysis"))))
+        gtk_window_set_child (main_window, GTK_WIDGET (get_window_child_DATA())); // window_main_child (main_window, DATA);
 }// SWITCH_TO (DATA);}
 
 
diff --git a/contain.c b/contain.c
index ac29708..7f41663 100644
--- a/contain.c
+++ b/contain.c
@@ -244,44 +244,10 @@ void window_header_bar (GtkWindow *window, char *title){
 //  ma préférée : Transport Steam Engine Icon     mais : [ process icon ]  semble un bon choix...
 }
 
-void window_main_child (GtkWindow *main_window, int selected_page){
-//  in  automaton.h :  enum { INTER, STATE, RULES, DATA }
-    if (0) printf ("window_main_child()   selected_page = %d\n", selected_page);
-
-  switch (selected_page) {
-  case (INTER) : //SWITCH_TO (INTER);
-  break;
-  case (STATE) :
-    //  printf ("SWITCH_TO STATE\n");
-    GtkBox *page_box = GTK_BOX (gtk_box_new (GTK_ORIENTATION_VERTICAL, 2));
-    gtk_box_append (page_box, GTK_WIDGET (get_OBJECTS_and_SITUATIONS()));
-    gtk_box_append (page_box, GTK_WIDGET (gtk_separator_new (GTK_ORIENTATION_HORIZONTAL)));
-    gtk_box_append (page_box, GTK_WIDGET (get_SPACE_VIEW_box()));
-    gtk_box_append (page_box, GTK_WIDGET (gtk_separator_new (GTK_ORIENTATION_HORIZONTAL)));
-//    window_main_child_bottom (page_box);
-//    if (!get_mode ()) gtk_box_append (page_box, GTK_WIDGET (get_TIME_EXEC_controls_box()));
-//    else             gtk_box_append (page_box, GTK_WIDGET (get_SPACE_EDIT_controls_box()));
-    gtk_window_set_child (main_window, GTK_WIDGET (page_box));
-    //SWITCH_TO (STATE);
-  break;
-  case (RULES) :  gtk_window_set_child (main_window, GTK_WIDGET (get_rules_page_new()));
-  //  printf ("SWITCH_TO RULES\n");
-  break;
-  case (DATA)  :  gtk_window_set_child (main_window, GTK_WIDGET (get_window_child_DATA()));
-  //  printf ("SWITCH_TO DATA\n");
-  break;
-  case (4) :  gtk_window_set_child (main_window, GTK_WIDGET (get_results_page_new())); break;
-  case (5) :  gtk_window_set_child (main_window, GTK_WIDGET (get_discuss_page_new())); break;
-  case (6) :  gtk_window_set_child (main_window, GTK_WIDGET (get_help_page_new())); break;
-  default :   gtk_window_set_child (main_window, GTK_WIDGET (get_SPACE_VIEW_box())); // + un "help message"
-  }
-  //  printf ("%d\n", get_status());
-}
-
 void main_window_design (GtkWindow *main_window){
   window_header_bar (main_window,
                      "E coli   (with permission from David S. Goodsell, 2009)");
-  window_main_child (main_window, STATE);
+  gtk_window_set_child (main_window, GTK_WIDGET (get_window_child_STATE()));  //  window_main_child (main_window, STATE);
 //  set_check_button_active (GTK_BUTTON (btt_open_STATE), 1);
   gtk_window_present (GTK_WINDOW (main_window));
 }
@@ -368,6 +334,30 @@ static void icons_for_fun (GtkHeaderBar *header_bar)
   gtk_header_bar_pack_end (header_bar, GTK_WIDGET (power_low));
 }
 
+GtkWidget *get_window_child_STATE() {
+    GtkBox *page_box = GTK_BOX (gtk_box_new (GTK_ORIENTATION_VERTICAL, 2));
+    gtk_box_append (page_box, GTK_WIDGET (get_OBJECTS_and_SITUATIONS()));
+    gtk_box_append (page_box, GTK_WIDGET (gtk_separator_new (GTK_ORIENTATION_HORIZONTAL)));
+    gtk_box_append (page_box, GTK_WIDGET (get_SPACE_VIEW_box()));
+    gtk_box_append (page_box, GTK_WIDGET (gtk_separator_new (GTK_ORIENTATION_HORIZONTAL)));
+    if (!get_mode ()) gtk_box_append (page_box, GTK_WIDGET (get_TIME_EXEC_controls_box()));
+    else              gtk_box_append (page_box, GTK_WIDGET (get_SPACE_EDIT_controls_box()));
+    //SWITCH_TO (STATE);
+    return GTK_WIDGET (page_box);
+}
+
+GtkWidget *get_window_child_RULES(){
+  GtkPaned *H_tree_vs_selected = GTK_PANED (gtk_paned_new (GTK_ORIENTATION_HORIZONTAL));
+//  GtkWidget *arbre_des_règles = gtk_frame_new ("Arbre des règles");
+//  GtkWidget *édition_de_la_règle_sélectionnée_n_1 = gtk_frame_new ("Inspection");
+  gtk_paned_set_start_child (H_tree_vs_selected, GTK_WIDGET (get_rules_tree_hpaned_new()));
+  gtk_paned_set_end_child (H_tree_vs_selected, GTK_WIDGET (get_selected_rules_vpaned_new()));
+  gtk_paned_set_position (H_tree_vs_selected, 400); //  WARNING : c'est une position "absolue"
+  gtk_paned_set_wide_handle (H_tree_vs_selected, TRUE);
+    //SWITCH_TO (RULES);
+  return GTK_WIDGET (H_tree_vs_selected);
+}
+
 GtkWidget *get_window_child_DATA (){
   GtkBox *data_box = GTK_BOX (gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 32));
 
@@ -463,6 +453,7 @@ GtkWidget *get_window_child_DATA (){
   gtk_box_append (help_box, GTK_WIDGET (gtk_separator_new (GTK_ORIENTATION_HORIZONTAL)));
   gtk_box_append (help_box, gtk_button_new_with_label ("preferences"));
 
-    return GTK_WIDGET (data_box);
+  //SWITCH_TO (DATA);
+  return GTK_WIDGET (data_box);
 }
 
diff --git a/contain.h b/contain.h
index a0e382c..64fb6df 100644
--- a/contain.h
+++ b/contain.h
@@ -35,7 +35,9 @@ void two_notebooks_in_two_panes (GtkWindow *window);
 GtkWidget *get_selected_rules_vpaned_new();
 GtkFrame *get_frame_with_label();
 void window_main_child_bottom (GtkBox *page_box);
-void window_main_child (GtkWindow *main_window, int selected_page);
+//void window_main_child (GtkWindow *main_window, int selected_page);
 void set_check_button_active (GtkButton *button, int active);
 GtkButton *get_GtkButton (char *btt_name);
+GtkWidget *get_window_child_STATE();
+GtkWidget *get_window_child_RULES();
 GtkWidget *get_window_child_DATA();
diff --git a/display.h b/display.h
index 90cf07a..157190b 100644
--- a/display.h
+++ b/display.h
@@ -21,6 +21,7 @@ GtkWidget *get_image_PHENYLALANINE();
 GtkWidget *get_image_DOPAMINE();
 GtkWidget *get_image_ATP();
 GtkWidget *get_image_AMP();
+GtkWidget *get_rules_tree_hpaned_new();
 
 GtkProgressBar *get_ELAPSED_TIME_ProgressBar();
 GtkBox *get_RUN_STOP_box();