Janssen created the first microscope. It had a 3x magnification but when extended, could reach up to 10x ("History of the Microscope", 2010)
Discovery of Cells
Robert Hooke, studying thin slices of cork, discovered box-like structures he called "cells". They were called cells because the structure reminded him of the cells of a monastery("History of the Microscope", 2010).
Discovery of Unicellular Organisms
Anton van Leeuwenhoek created a powerful microscope, and with it, discovered the existence of unicellular organisms.
Plants are made of cells
Matthias Schleiden states that all plants are made of cells.
Animals are made of cells
Theodore Schwann states that all animals are made of cells.
Cells come from cells
Rudolf Virchow states that all cells come from preexisting cells.
Revolution of Optical Instruments
Carl Zeiss, Ernst Abbe, and Otto Schott revolutionized the manufacture of optical instruments and invented the modern compound microscope.
Invention of the Electron Microscope
Max Knoll and Ernst Ruska invented the electron microscope. With it, they were able to see even atoms.