Structure of squares

Take a look at the animation below.

Can you describe what happens?

The animation shows that $1 + 3 + 5 + 7 = 16$.

Can you use the animation to deduce a quick way of working out the sum of the first 10 odd numbers?

What about the first 50 odd numbers?

Can you make the number $3249$ by adding up a sequence of odd numbers?