diff --git a/mapytex/calculus/API/__init__.py b/mapytex/calculus/API/__init__.py
index 8d74ae3..5db61aa 100644
--- a/mapytex/calculus/API/__init__.py
+++ b/mapytex/calculus/API/__init__.py
@@ -84,15 +84,14 @@ x^7
 >>> e = Expression.from_str("1+2x^2+3x+4+5x")
 >>> e_simplified = e.simplify()
 >>> print(e_simplified)
-2x^2 + 5 + 8x
+5 + 2x^2 + 8x
 >>> for s in e_simplified.explain():
 ...    print(s)
 1 + 2x^2 + 3x + 4 + 5x
-2x^2 + 3x + 1 + 4 + 5x
-3x + 5 + 2x^2 + 5x
-2x^2 + 3x + 5x + 5
-2x^2 + (3 + 5) * x + 5
-2x^2 + 5 + 8x
+1 + 2x^2 + 3x + 4 + 5x
+1 + 4 + 2x^2 + 3x + 5x
+5 + 2x^2 + (3 + 5) * x
+5 + 2x^2 + 8x
 
 
 """
@@ -100,9 +99,19 @@ x^7
 from .expression import Expression
 
 if __name__ == "__main__":
-    e = Expression.from_str("2+3/4")
-    e_simplified = e.simplify()
-    print(e_simplified)
+    e = Expression.from_str("1+2/3/4/5")
+    et = e._typing()
+    print("typing")
+    print(e._tree)
+    e = et._order()
+    print("order")
+    print(e._tree)
+    e = e._optimize()
+    print("then optimize")
+    print(e._tree)
+    e = et._optimize()
+    print("optimize without order")
+    print(e._tree)
 
 # -----------------------------
 # Reglages pour 'vim'
diff --git a/mapytex/calculus/API/expression.py b/mapytex/calculus/API/expression.py
index 660ec91..d06a608 100644
--- a/mapytex/calculus/API/expression.py
+++ b/mapytex/calculus/API/expression.py
@@ -88,7 +88,45 @@ class Expression(object):
     def __repr__(self):
         return f"<Exp: {renders[self.RENDER](self._tree)}>"
 
-    def _optimize(self, exclude_nodes=["\\", "**"]):
+    def _order(self, exclude_nodes=["*", "/", "**"]):
+        """ Order the expression base on types
+
+        :example:
+        
+        >>> e = Expression.from_str("1 + 2x + 3 + 4x")
+        >>> print(e)
+        1 + 2x + 3 + 4x
+        >>> #print(e._order())
+        1 + 3 + 2x + 4x
+        >>> e = Expression.from_str("x + 6x^3 + 1 + 2x^2 + 3 + 4x^2 + 5x")
+        >>> print(e._order())
+        x + 5x + 6x^3 + 2x^2 + 4x^2 + 1 + 3
+        """
+        def signature(leaf):
+            try:
+                leaf.node
+            except AttributeError:
+                try:
+                    return leaf.signature
+                except AttributeError:
+                    return type(leaf)
+            else:
+                try:
+                    typed_leaf =  typing(leaf.node, leaf.left_value, leaf.right_value)
+                    return typed_leaf.signature
+                except (AttributeError, NotImplementedError, TypingError):
+                    return type(leaf)
+
+        try:
+            self._tree.node
+        except AttributeError:
+            return self
+
+        organised = AssocialTree.from_any_tree(self._tree).\
+            organise_by(signature, recursive=True, exclude_nodes=exclude_nodes)
+        return Expression(organised)
+
+    def _optimize(self, exclude_nodes=["/", "**"]):
         """ Return a copy of self with an optimize tree
         
         :example:
@@ -199,7 +237,8 @@ class Expression(object):
         typed_exp = self._typing()
 
         if optimize:
-            opt_exp = typed_exp._optimize()
+            organized_exp = typed_exp._order()
+            opt_exp = organized_exp._optimize()
         else:
             opt_exp = typed_exp
 
@@ -228,9 +267,9 @@ class Expression(object):
         >>> for s in f.explain():
         ...     print(s)
         1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
-        3 + 3 + 9 + 6 + 7 + 17
-        6 + 9 + 6 + 24
-        15 + 30
+        3 + 7 + 11 + 7 + 17
+        10 + 11 + 24
+        10 + 35
         45
         >>> e = Expression.from_str("1+2+3+4+5+6+7+8+9")
         >>> f_no_balance = e.simplify(optimize=False)
@@ -250,10 +289,11 @@ class Expression(object):
         >>> for s in f.explain():
         ...     print(s)
         1 + 2 + 3 + 4 + 5 * 6 * 7 * 8 * 9
-        3 + 3 + 4 + 30 * 7 * 72
-        6 + 4 + 210 * 72
+        3 + 7 + 30 * 7 * 72
+        10 + 210 * 72
         10 + 15120
         15130
+
         >>> e = Expression.from_str("1+2+3+4+5*6*7*8*9")
         >>> f_no_balance = e.simplify(optimize=False)
         >>> for s in f_no_balance.explain():