The statement, "all plants and animal tissue is made up of tiny units," is known as the what?

The Cell Theory states that all plants and animal tissue are made up of tiny units. It is one of the most basic principles of Biology. Theodor Schwann, Matthias Schleiden, and Rudolph Virchow were credited for this theory. 

The Cell Theory states that cells are the basic unit or the building blocks of life and that all cells existed or arose from pre-existing cells. The theory also states that all living organisms are made up of either unicellular or multicellular cells that have energy flow and are responsible for many processes in the bodies of living organisms.

The modern definition of the theory is that all cells have the same basic compositions and DNA is passed on from cell to cell.  

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