diff --git a/pymath/calculus/abstract_polynom.py b/pymath/calculus/abstract_polynom.py
index 5e0bfcd..6faab70 100644
--- a/pymath/calculus/abstract_polynom.py
+++ b/pymath/calculus/abstract_polynom.py
@@ -156,7 +156,6 @@ class AbstractPolynom(Explicable):
         ['x', 2, '^']
 
         """
-        # TODO: Couille certaine avec txt à qui il fait donner des opérateurs tout beau! |mar. nov. 11 13:08:35 CET 2014
         ans =[] 
         if a == [0]:
             pass
@@ -309,37 +308,46 @@ class AbstractPolynom(Explicable):
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [3, 12, 6]>
         >>> for i in Q.explain():
         ...     print(i)
+        6 x^{  2 } + 3 x + 4 x + 5 x + 1 + 2
         6 x^{  2 } + ( 3 + 4 + 5 ) x + 1 + 2
         6 x^{  2 } + ( 7 + 5 ) x + 3
         6 x^{  2 } + 12 x + 3
         >>> Q.steps
-        [< <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [< <class 'pymath.calculus.expression.Expression'> [1, 2, '+'] >, < <class 'pymath.calculus.expression.Expression'> [3, 4, '+', 5, '+'] >, 6]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [3, < <class 'pymath.calculus.expression.Expression'> [7, 5, '+'] >, 6]>]
+        [< <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [[1, 2], [3, 4, 5], 6]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [< <class 'pymath.calculus.expression.Expression'> [1, 2, '+'] >, < <class 'pymath.calculus.expression.Expression'> [3, 4, '+', 5, '+'] >, 6]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [3, < <class 'pymath.calculus.expression.Expression'> [7, 5, '+'] >, 6]>]
         """
     
         # TODO: It doesn't not compute quick enough |ven. févr. 27 18:04:01 CET 2015
 
-        # gather steps for every coeficients
+        # gather steps for every coefficients
         coefs_steps = []
         for coef in self._coef:
             coef_steps = []
-            if type(coef) == list:
-                # On converti en postfix avec une addition
-                postfix_add = self.postfix_add([i for i in coef if i!=0])
-                # On converti en Expression
+
+            if type(coef) ==list:
+                # Simplify each element before adding them
+                s = []
+                for c in coef:
+                    try:
+                        with Expression.tmp_render():
+                            s.append(list(c.simplify().explain()))
+                    except AttributeError:
+                        s.append([c])
+
+                s = list(transpose_fill(s))
+
+                last = s[-1]
+                coef_steps += s
+
+                # Convert last element into postfix addition.
+                postfix_add = self.postfix_add([i for i in last if i!=0])
+                # Convert it to an expression
                 coef_exp = Expression(postfix_add)
 
                 with Expression.tmp_render():
-                    coef_steps = list(coef_exp.simplify().explain())
+                    coef_steps += list(coef_exp.simplify().explain())
 
                 #print('\t 1.coef_steps -> ', coef_steps)
 
-            elif type(coef) == Expression:
-
-                with Expression.tmp_render():
-                    coef_steps = list(coef.simplify().explain())
-
-                #print('\t 2.coef_steps -> ', coef_steps)
-
             else:
                 try:
                     with Expression.tmp_render():
@@ -408,8 +416,14 @@ class AbstractPolynom(Explicable):
         >>> R = P+Q
         >>> R
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [5, 7, 3]>
+        >>> for i in R.explain():
+        ...    print(i)
+        3 x^{  2 } + 2 x + 1 + 5 x + 4
+        3 x^{  2 } + 2 x + 5 x + 1 + 4
+        3 x^{  2 } + ( 2 + 5 ) x + 1 + 4
+        3 x^{  2 } + 7 x + 5
         >>> R.steps
-        [< <class 'pymath.calculus.expression.Expression'> [3, 'x', 2, '^', '*', 2, 'x', '*', '+', 1, '+', 5, 'x', '*', 4, '+', '+'] >, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [< <class 'pymath.calculus.expression.Expression'> [1, 4, '+'] >, < <class 'pymath.calculus.expression.Expression'> [2, 5, '+'] >, 3]>]
+        [< <class 'pymath.calculus.expression.Expression'> [3, 'x', 2, '^', '*', 2, 'x', '*', '+', 1, '+', 5, 'x', '*', 4, '+', '+'] >, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [[1, 4], [2, 5], 3]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [< <class 'pymath.calculus.expression.Expression'> [1, 4, '+'] >, < <class 'pymath.calculus.expression.Expression'> [2, 5, '+'] >, 3]>]
         """
         o_poly = self.conv2poly(other)
 
@@ -448,14 +462,15 @@ class AbstractPolynom(Explicable):
         >>> R = P - Q
         >>> R
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [-3, -3, -3]>
-        >>> R.steps
-        [< <class 'pymath.calculus.expression.Expression'> [3, 'x', 2, '^', '*', 2, 'x', '*', '+', 1, '+', 6, 'x', 2, '^', '*', 5, 'x', '*', '+', 4, '+', '-'] >, < <class 'pymath.calculus.expression.Expression'> [3, 'x', 2, '^', '*', 2, 'x', '*', '+', 1, '+', 6, 'x', 2, '^', '*', '-', 5, 'x', '*', '-', 4, '-', '+'] >, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [< <class 'pymath.calculus.expression.Expression'> [1, -4, '+'] >, < <class 'pymath.calculus.expression.Expression'> [2, -5, '+'] >, < <class 'pymath.calculus.expression.Expression'> [3, -6, '+'] >]>]
         >>> for i in R.explain():
         ...     print(i)
         3 x^{  2 } + 2 x + 1 - ( 6 x^{  2 } + 5 x + 4 )
         3 x^{  2 } + 2 x + 1 -  6 x^{  2 } - 5 x - 4
+        3 x^{  2 } - 6 x^{  2 } + 2 x - 5 x + 1 - 4
         ( 3 - 6 ) x^{  2 } + ( 2 - 5 ) x + 1 - 4
         - 3 x^{  2 } - 3 x - 3
+        >>> R.steps
+        [< <class 'pymath.calculus.expression.Expression'> [3, 'x', 2, '^', '*', 2, 'x', '*', '+', 1, '+', 6, 'x', 2, '^', '*', 5, 'x', '*', '+', 4, '+', '-'] >, < <class 'pymath.calculus.expression.Expression'> [3, 'x', 2, '^', '*', 2, 'x', '*', '+', 1, '+', 6, 'x', 2, '^', '*', '-', 5, 'x', '*', '-', 4, '-', '+'] >, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [[1, -4], [2, -5], [3, -6]]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [< <class 'pymath.calculus.expression.Expression'> [1, -4, '+'] >, < <class 'pymath.calculus.expression.Expression'> [2, -5, '+'] >, < <class 'pymath.calculus.expression.Expression'> [3, -6, '+'] >]>]
         """
         o_poly = self.conv2poly(other)
         ini_step = [Expression(self.postfix_tokens + o_poly.postfix_tokens + [op.sub])]
@@ -501,7 +516,6 @@ class AbstractPolynom(Explicable):
         >>> P*Q
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [4, 13, 28, 27, 18]>
         """
-        # TODO: Je trouve qu'elle grille trop d'étapes... |ven. févr. 27 19:08:44 CET 2015
         o_poly = self.conv2poly(other)
 
         coefs = [0]*(self.degree + o_poly.degree + 1)
@@ -549,7 +563,7 @@ class AbstractPolynom(Explicable):
         >>> p**2
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [1, 4, 4]>
         >>> (p**2).steps
-        [< <class 'pymath.calculus.expression.Expression'> [2, 'x', '*', 1, '+', 2, '^'] >, [< <class 'pymath.calculus.expression.Expression'> [2, 'x', '*', 1, '+', 2, 'x', '*', 1, '+', '*'] >], < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [1, < <class 'pymath.calculus.expression.Expression'> [2, 2, '+'] >, < <class 'pymath.calculus.expression.Expression'> [2, 2, '*'] >]>]
+        [< <class 'pymath.calculus.expression.Expression'> [2, 'x', '*', 1, '+', 2, '^'] >, [< <class 'pymath.calculus.expression.Expression'> [2, 'x', '*', 1, '+', 2, 'x', '*', 1, '+', '*'] >], < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [1, [2, 2], < <class 'pymath.calculus.expression.Expression'> [2, 2, '*'] >]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [1, < <class 'pymath.calculus.expression.Expression'> [2, 2, '+'] >, 4]>]
         >>> p = AbstractPolynom([0,0,1])
         >>> p**3
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [0, 0, 0, 0, 0, 0, 1]>