The cell was discovered when people started looking through the earliest microscopes. Robert Hooke looked at cork, which is the bark of the cork oak, and its cells are dead. The walls of the dead cells looked like the rooms, or cells, of monks, so he called them cells.
The cell was first discovered and named by Robert Hooke in 1665. He remarked that it looked strangely similar to cellula or small rooms which monks inhabited, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cells(cork) as it appeared under the microscope.