I owned this book in the late 1980’s. It is a science book for children. Throughout the book, there are illustrations that include little cartoon scientists with mustaches (and glasses?). The only illustration I can actually remember is a microscope with the parts labeled and little mustachioed scientists climbing on it and looking at it. It was hardcover (no book jacket, just a glossy illustrated cover) and maybe about 1. 5 cm thick. The illustrations struck me as somewhat “European”.
Could this be How Things Work? There are little men in all of the diagrams.
Sorry, I meant, The Way Things Work by David Macauley.
Thanks, Leah, but that is not it. I think it was more Biology-centered.