How the cell was discovered?

In 1665, the English Botanist, 'Robert Hooke' observed cells by viewing the cell walls of a cork slice(the bark of the cork oak) through a primitive compound microscope and discovered a honeycomb structure in the dead cell walls of plant cells(cork). 

It was appearing like many tiny pores and he named them "cells".

 

The word "cell" was taken from the Latin word 'Cella', which means 'a small room or compartment' and also Cellular, which means the six-sided cell of a honeycomb.