Falling object/images to form one in the end

[size=2]If let’s say I have a 3 parts image, ( bottom, middle and top )and I want all 3 parts to come down one by one on top of each other on my page to form a box. How would I go about it?
Different layer for all 3 parts that much I know, but that’s about it.

Hope someone understands what I mean and thanks for the help :))