Answer:
The cell was first discovered by Robert Hooke in 1665 using a microscope.
The first cell theory is credited to the work of Theodor Schwann and Matthias Jakob Schleiden in the 1830s.
Hooke had discovered plant cells -- more precisely, what Hooke saw were the cell walls in cork tissue. In fact, it was Hooke who coined the term "cells": the boxlike cells of cork reminded him of the cells of a monastery.
