Cells were first seen in cork, a plant material.

Here's the breakdown:

* Robert Hooke, an English scientist, was the first to observe and name cells in 1665.

* He used a crude microscope to examine a thin slice of cork from the bark of a tree.

* He saw small, box-like compartments that he named "cells" because they reminded him of the small rooms monks lived in, called cells.

* While Hooke didn't realize he was looking at living cells, his discovery was a crucial step in understanding the basic structure of life.