Where did the puzzle piece for autism come from, and why do they use a puzzle piece?

The infamous bongblaster: Where did the puzzle piece for autism come from, and why do they use a puzzle piece?
I was driving today and seen an autism awareness sticker, a puzzle piece. I was wondering why a puzzle piece was used to represent it, and where did it originate?

Answers and Views:

Answer by Chatterbox F
it’s hard to explain…my brother has autism and i think basically the puzzle pieces show how different each and every one of them are, and that we are still trying to make the pieces fit together, as in make sense of how and why this disability is what it is.

Answer by Snuffy
The puzzle piece represents the piece of the brain that is missing so to speak.