When Alan Kay was a graduate student, he thought about the way we conventionally think of computers, and decided it was very strange. Why break a system down into parts that indivdually were so weak and useless.
In mathematics there was an idea that was just becoming popular at this time named fracticals. The key idea of fractals is that a system will look the same at any level of resolution. Think of brocolli -- a clump of brocolli looks like an individual piece, which looks like the fingers that build up the individual piece, an so on.
So kay thought; why can't we structure a computer by building it out of little computers.