in which specimen were cells first identified?

Cells were first identified in a specimen of cork. Robert Hooke was examining a thin slice of cork bark using a primitive microscope in 1665 when he observed small, box-like compartments, which he named "cells" because they resembled the small rooms (cellula) inhabited by monks. However, what Hooke actually saw were the dead cell walls of the cork plant tissue, not living cells themselves. This discovery marked the first identification of cells using a microscope.