diff --git a/src/ui/sand_box.c b/src/ui/sand_box.c
index 1a6ca1f..66ecc36 100644
--- a/src/ui/sand_box.c
+++ b/src/ui/sand_box.c
@@ -136,6 +136,9 @@ setup_tree (void)
 
 }
 
+static void on_activating_this_expander (GtkExpander *my_expander, gpointer my_data){}
+
+
 //  -------------   End Matthias Clasen   --------------------------------------
 
 enum { COLUMN_DESCRIPTION };
@@ -191,7 +194,9 @@ static void and_now_let_s_climb_that_tree (GtkWidget *in_that_box)
     gtk_tree_view_append_column (GTK_TREE_VIEW (my_tree_view), my_column);    gtk_tree_store_set (my_list_store, &child_iter, my_column, "two", -1);
 
     GtkWidget *my_expander = gtk_expander_new ("my_expander");
-    printf("%s\n", gtk_expander_get_label (my_expander));
+    gtk_expander_set_child (my_expander, NULL); //  *child);    how to ?
+    on_activating_this_expander (my_expander, NULL);  //     gpointer     user_data)   The “activate” signal
+    printf("%s\n", gtk_expander_get_label (my_expander));   //  <  OK
 
     //  GtkWidget my_column = *gtk_column_view_new (my_selection_model);
     /* GtkWidget *treeview; */