Zacharias Janssen and his father, Hans, were eyeglass makers. In 1590, they created the first microscope.
Robert Hooke made his own microscope. It's light was an oil lamp, and the lens focused the lamp's light onto the specimen.
Hooke looked at a slice of cork under a microscope. He saw little boxes that reminded him of a monk's room at a monastery. Thus, he named them "cells."
Anton looked at samples of water under microscopes. He found many single-celled organisms. They moved around, hopped and jumped, and shot through the water like fast fish. Anton named them "animalcules". Animalcules means little animals.
Matthias studied plants under a microscope and found out that plants also have cells.
Theodor Schwann studies animals and discovered that they were also made of cells. He looked at other peoples' research and concluded that all living things are made of cells.
Rudolph Virchow found out that new cells are formed from old cells. This was important because no one else had explained where cells came from.