The cell theory states that the cell is the basic unit of life. Hans and Zacharias Jansen greatly contributed to the various parts of this theory by inventing the first microscope.
The cell theory also states that all living organisms are composed of cells. Organisms can be unicellular or multicellular. The theory states that all cells arise from pre-existing cells, according to About.com. Zacharias Jansen, a Dutch spectacle maker, invented the first compound microscope around 1590. Hans Jansen, Zacharias's father, was believed to have assisted in the creation of this young scientist's invention. The first microscope consisted of three draw tubes with lenses inside the ends. This microscope was complex for its time. The design consisted of a bi-convex eyepiece lens and a plano-convex objective lens. Magnifying images was achieved by sliding the draw tube in or out while focusing on the sample. When the tubes were extended to the maximum length, the microscope was able to magnify a sample up to 10 times the original size. The invention of this scientific instrument allowed Robert Hooke and Anton van Leeuwenhoek, notable scientists of the late 17th century, to observe diatoms, fossils and the first cells. The invention of the compound microscope laid the foundation for the advancement in microscopy.