list comprehensions whats happening here

[zzzzz]

While trying to remember the correct syntax for list comprehensions I
stumbled upon the following results, can anyone enlighten me as to
what is going on here?

>>> [[i,j] for i in range(3), for j in range(3)]
[[[0, 1, 2], 0], [[0, 1, 2], 1], [[0, 1, 2], 2]]

>>> [[i,j] for i in range(3), for j in range(3),]
[[[0, 1, 2], [0, 1, 2]]]

Here I finally got it right:

>>> [[i,j] for i in range(3) for j in range(3)]
[[0,0],[0,1],[0,2],[1,0],[1,1],[1,2],[2,0],[2,1],[2,2]]