Timeline – The Microscope & The Cell Theory!
1214 – 1294
Roger Bacon used a convex lens as a magnifying glass.
Leonardo De Vinci stressed the importance of using lenses for the study of small objects.
Hans & Zacharias Janssen
Two Dutch lens makers, a father and son, Hans and Zacharias Janssen, are credited having made the first compound microscope. Since Janssen was very young at that time, it is possible that his father Hans made the first one, but Zacharias perfected the production. A simple microscope uses only one lens to magnify an object viewed so the invention of the compound microscope relied on the principle of using two lenses, kept a set distance apart.
The name microscope was first used for magnifying instruments. The word microscope comes from the words ‘mikros’ meaning small and ‘skopeo’ meaning ‘to look at.
Redi postulated that living things do not arise from spontaneous generation.
Robert Hooke
1663 – 1665
In 1665, Robert Hooke produced a book a book, the first recorded publication to describe observations of living tissue using a microscope. It was titled, Micrographia: physiological studies of minute bodies made by magnifying glasses.   The book contained many drawings of specimens he had examined under the microscope, including cork, stinging nettle and a flea. The structure of the cork, with its rectangular units lined up side-by-side, reminded Hooke of small rooms or ‘cells’ in a monastery. Thus, the building block of living matter was named the ‘cell’. Hooke’s findings were respected, but not universally accepted by scientists at that time.
The microscopes used by Hooke had two lenses fitted to either end of a barrel. The microscope was focused by rotating the barrel up or down on a screw thread. A glass sphere filled with water was used to focus light from an oil lamp onto the specimen.
Marcello Malpighi stated that all plants are built of chambers.
Anton Van Leeuwenhoek
1674 - 1683