diff --git a/numpy/numpy.ipynb b/numpy/numpy.ipynb
index 852a696..0436f89 100644
--- a/numpy/numpy.ipynb
+++ b/numpy/numpy.ipynb
@@ -442,6 +442,143 @@
       }
      ],
      "prompt_number": 19
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "## Combining Arrays"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "a"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 20,
+       "text": [
+        "array([1, 2, 3])"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "b"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 21,
+       "text": [
+        "array([[0, 2, 4],\n",
+        "       [1, 3, 5]])"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "d"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 22,
+       "text": [
+        "array([[ 1. ,  3. ,  5. ],\n",
+        "       [ 1.5,  3.5,  5.5]])"
+       ]
+      }
+     ],
+     "prompt_number": 22
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "np.concatenate([a, a, a])"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 23,
+       "text": [
+        "array([1, 2, 3, 1, 2, 3, 1, 2, 3])"
+       ]
+      }
+     ],
+     "prompt_number": 23
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "# Use broadcasting when needed to do this automatically\n",
+      "np.vstack([a, b, d])"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 24,
+       "text": [
+        "array([[ 1. ,  2. ,  3. ],\n",
+        "       [ 0. ,  2. ,  4. ],\n",
+        "       [ 1. ,  3. ,  5. ],\n",
+        "       [ 1. ,  3. ,  5. ],\n",
+        "       [ 1.5,  3.5,  5.5]])"
+       ]
+      }
+     ],
+     "prompt_number": 24
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "# In machine learning, useful to enrich or \n",
+      "# add new/concatenate features with hstack\n",
+      "np.hstack([b, d])"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 25,
+       "text": [
+        "array([[ 0. ,  2. ,  4. ,  1. ,  3. ,  5. ],\n",
+        "       [ 1. ,  3. ,  5. ,  1.5,  3.5,  5.5]])"
+       ]
+      }
+     ],
+     "prompt_number": 25
     }
    ],
    "metadata": {}