title: Very Basic Numpy array dimension visualization
body: <p>I'm a beginner to numpy with no experience in matrices. I understand basic 1d and 2d arrays but I'm having trouble visualizing a 3d numpy array like the one below. How do the following python lists form a 3d array with height, length and width? Which are the rows and columns?</p>
  
  <pre><code>b = np.array([[[1, 2, 3],[4, 5, 6]],
            [[7, 8, 9],[10, 11, 12]]])
  </code></pre>