There was a horticulture textbook that showed a zoomed-out plot of land on the cover, which with its divisions and sectional diversity effectively looked something like an illustration of the inside of a CPU.
It wasn't intentional as far as I know, but I have to admit that stuck in my head ever since as a really eye-opening metaphor. And the contents of the book were really new to me and even more eye-opening.
Wish I had the name of the book, sorry.