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1590
Zacharias Janssen and his neighbour Hans placed multiple lenses in a tube. They observed that viewed objects in front of the tube appeared to be enlarged. -
English physicist Robert Hooke published Micrographia, in which he coined the term ‘cells’ when he was describing tissue. The book included drawings of hairs on a nettle and the honeycomb structure of cork. He used a simple, single-lens microscope illuminated by a candle.
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Antonie van Leeuwenhoek built a simple microscope with one lens to examine blood, yeast and insects. He was the first to describe cells and bacteria. He invented new methods for making lenses that allowed magnifications of up to 270 times.
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In 1838, Matthias Schleiden, a German botanist, concluded that all plant tissues are composed of cells and that an embryonic plant arose from a single cell. He declared that the cell is the basic building block of all plant matter.
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In 1839, Theodor Schwann, a German biologist, reached the same
conclusion as Schleiden about animal tissue being composed of cells, ending speculations that plants and animals were different in structure. -
In 1855, the German physiologist, physician, pathologist, and
anthropologist Rudolf Virchow was able to add a third part to the cell
theory. He stated that all cells develop only from existing cells. Virchow was the first to demonstrate that the cell theory applies to diseased tissue well as to healthy tissue.