Cells were discovered by Robert Hooke in 1665.

Hooke, an English scientist, was examining a thin slice of cork using a microscope he had built. He observed small, box-like compartments, which reminded him of the cells in a monastery. As such, he termed the compartments "cells."

It is important to note that Hooke only observed the cell walls, as cork cells are dead. He did not see the cell nucleus or other internal components. The discovery and subsequent study of cells marked a pivotal moment in biology, leading to the development of cell theory.