In 1665, Hooke was observing a thin slice of cork under a microscope he built. He noticed small, box-like compartments that reminded him of the cells in a honeycomb. He called these compartments "cells" because of their resemblance.

While Hooke wasn't the first to use a microscope, his observations and the term "cell" he coined revolutionized our understanding of living organisms and laid the foundation for the field of cell biology.