diff --git a/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb b/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
index 28a4c83..bedbf77 100644
--- a/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
+++ b/.ipynb_checkpoints/not_so_obvious_python_stuff-checkpoint.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:257a5a05fdf9f21f3a395d8edea0d549d6444deac97319a4c0c0d6478c490ece"
+  "signature": "sha256:65ce88feaf4030991defb4ffc22e758e20be8f6dc5dc3046d5c804aa0089de06"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -48,7 +48,7 @@
       "- [`bool` is a subclass of `int`](#bool_int)\n",
       "- [About lambda and closures-in-a-loop pitfall](#lambda_closure)\n",
       "- [Python's LEGB scope resolution and the keywords `global` and `nonlocal`](#python_legb)\n",
-      "- [When immutable Tuples aren't so immutable](#immutable_tuple)\n",
+      "- [When mutable contents of immutable tuples aren't so mutable](#immutable_tuple)\n",
       "- [List comprehensions are fast, but generators are faster!?](#list_generator)"
      ]
     },
@@ -830,17 +830,16 @@
       "<br>\n",
       "<br>\n",
       "<a name='immutable_tuple'></a>\n",
-      "## When immutable Tuples aren't so immutable"
+      "## When mutable contents of immutable tuples aren't so mutable"
      ]
     },
     {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "As we all know, tuples are immutable objects in Python, right!?\n",
+      "As we all know, tuples are immutable objects in Python, right!? But what happens if they contain mutable objects? \n",
       "\n",
-      "**Note:** As a careful reader pointed out,  \n",
-      "\"The tuple is still immutable. You were unable to change it's cardinality, or trick it into pointing to a different contained object.\""
+      "First, let us have a look at the expected behavior: a `TypeError` is raised if we try to modify a value tuple: "
      ]
     },
     {
@@ -870,7 +869,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a type error, funny, isn't it?"
+      "#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a `TypeError` at the same time."
      ]
     },
     {
@@ -929,7 +928,7 @@
      "source": [
       "<br>\n",
       "<br>\n",
-      "However, there **IS** a way (where there should be none!) to modify our immutable tuple without raising the `TypeError`, the solution is the `.extend()`:"
+      "However, **there are ways** to modify the mutable contents of the tuple without raising the `TypeError`, the solution is the `.extend()` method, or alternatively `.append()` (for lists):"
      ]
     },
     {
@@ -955,6 +954,29 @@
      ],
      "prompt_number": 44
     },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "tup = ([],)\n",
+      "print('tup before: ', tup)\n",
+      "tup[0].append(1)\n",
+      "print('tup after: ', tup)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "tup before:  ([],)\n",
+        "tup after:  ([1],)\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
     {
      "cell_type": "markdown",
      "metadata": {},
diff --git a/not_so_obvious_python_stuff.ipynb b/not_so_obvious_python_stuff.ipynb
index 28a4c83..bedbf77 100644
--- a/not_so_obvious_python_stuff.ipynb
+++ b/not_so_obvious_python_stuff.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:257a5a05fdf9f21f3a395d8edea0d549d6444deac97319a4c0c0d6478c490ece"
+  "signature": "sha256:65ce88feaf4030991defb4ffc22e758e20be8f6dc5dc3046d5c804aa0089de06"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -48,7 +48,7 @@
       "- [`bool` is a subclass of `int`](#bool_int)\n",
       "- [About lambda and closures-in-a-loop pitfall](#lambda_closure)\n",
       "- [Python's LEGB scope resolution and the keywords `global` and `nonlocal`](#python_legb)\n",
-      "- [When immutable Tuples aren't so immutable](#immutable_tuple)\n",
+      "- [When mutable contents of immutable tuples aren't so mutable](#immutable_tuple)\n",
       "- [List comprehensions are fast, but generators are faster!?](#list_generator)"
      ]
     },
@@ -830,17 +830,16 @@
       "<br>\n",
       "<br>\n",
       "<a name='immutable_tuple'></a>\n",
-      "## When immutable Tuples aren't so immutable"
+      "## When mutable contents of immutable tuples aren't so mutable"
      ]
     },
     {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "As we all know, tuples are immutable objects in Python, right!?\n",
+      "As we all know, tuples are immutable objects in Python, right!? But what happens if they contain mutable objects? \n",
       "\n",
-      "**Note:** As a careful reader pointed out,  \n",
-      "\"The tuple is still immutable. You were unable to change it's cardinality, or trick it into pointing to a different contained object.\""
+      "First, let us have a look at the expected behavior: a `TypeError` is raised if we try to modify a value tuple: "
      ]
     },
     {
@@ -870,7 +869,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a type error, funny, isn't it?"
+      "#### But what if we put a mutable object into the immutable tuple? Well, modification works, but we **also** get a `TypeError` at the same time."
      ]
     },
     {
@@ -929,7 +928,7 @@
      "source": [
       "<br>\n",
       "<br>\n",
-      "However, there **IS** a way (where there should be none!) to modify our immutable tuple without raising the `TypeError`, the solution is the `.extend()`:"
+      "However, **there are ways** to modify the mutable contents of the tuple without raising the `TypeError`, the solution is the `.extend()` method, or alternatively `.append()` (for lists):"
      ]
     },
     {
@@ -955,6 +954,29 @@
      ],
      "prompt_number": 44
     },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "tup = ([],)\n",
+      "print('tup before: ', tup)\n",
+      "tup[0].append(1)\n",
+      "print('tup after: ', tup)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "tup before:  ([],)\n",
+        "tup after:  ([1],)\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
     {
      "cell_type": "markdown",
      "metadata": {},