What is the Janssen Cell Theory by Hans and Zacharias Janssen?

The cell is the basic unit of life, according to the cell theory. By making the first microscope, Hans and Zacharias Jansen made a big contribution to many parts of this theory.

All living things are made up of cells, which is another part of the cell theory. Organisms can be unicellular or multicellular. About.com says that the theory says that all cells come from cells that were already there. Around 1590, a Dutch glasses maker named Zacharias Jansen made the first compound microscope.

Hans Jansen, Zacharias’s father, was thought to have helped this young scientist come up with his idea. The first microscope had lenses in the ends of three draw tubes. For its time, this microscope was pretty hard to use. A bi-convex eyepiece lens and a plano-convex objective lens were used to make the design.

By moving the draw tube in or out while focusing on the sample, images could be made bigger. When the tubes were all the way out, the microscope could make a sample up to 10 times bigger than it was before.

Robert Hooke and Anton van Leeuwenhoek, two famous scientists of the late 17th century, were able to study diatoms, fossils, and the first cells because of this scientific tool. The compound microscope was the first step in the field of microscopy moving forward.

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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