title: Why are the MNIST images 1x28x28 tensors?
body: <p>I made the MNIST images which are 28x28 pixel images into tensors with</p>
  <pre><code>dataset = MNIST(root='data/', train=True, transform=transforms.ToTensor())
  </code></pre>
  <p>and when I run</p>
  <pre><code>img_tensor, label = dataset[0]
  print(img_tensor.shape, label)
  </code></pre>
  <p>It says the shape is <code>torch.Size([1, 28, 28])</code>.
  Why is it a 1x28x28? What does the first dimension mean? and what is the point of a 1x28x28 opposed to 28x28?</p>