Robert Hooke's biological discovery about cells wasn't the discovery of the cell itself, but rather the first observation and naming of cells.

Here's what he did:

* 1665: Hooke used a primitive compound microscope to examine a thin slice of cork. He observed tiny, box-like compartments that reminded him of the cells in a honeycomb. He called these compartments "cells" because they looked like small rooms.

Important Note: Hooke was actually looking at the dead cell walls of the cork, not the living cells themselves. It was later, with improved microscopy, that scientists discovered the true nature and complexity of cells.