Observed nature directly. He classified all known organisms as either plants or animals.
Aristotle
Produced the first compound microscope by lining up 2 lenses.
Hans Janssen
Observed living matter from a piece of cork through a compound microscope, which reveals empty cells. He is the first to call the spaces in the cork “cells” which means little rooms.
Robert Hooke
Discovered that plants were made of cells.
Matthias Schleiden
States “all animals are made of cells.”
Theodore Schwann
Develops an intense purple dye, which is used to stain slides.
Hans Christian Gram
states that “Where a cell exists, there must have been a preexisting cell.”