A slice of cork under a microscope gave biology the word 'cell'

In 1665, Robert Hooke examined a thin sliver of cork under a microscope he built himself and saw tiny walled compartments, which reminded him of the small rooms monks lived in. He named them 'cells' in his book Micrographia, the term biology still uses for the basic unit of life. He was actually looking at dead plant cell walls, not living cells, but the name stuck for good.

— Robert Hooke, Micrographia — 1665