The discovery of cells first took place in the year:

The discovery of cells is attributed to the English scientist Robert Hooke, who observed a slice of cork under a primitive microscope in 1665. He found that the cork had a porous structure consisting of many small, empty spaces separated by walls, which he called "cells." Hooke's observation of the cork's honeycomb-like structure allowed him to realize that living organisms were composed of smaller, individual units, which he called cells. This discovery laid the foundation for the development of cell theory, which states that all living things are made up of cells.