The Three Superseded Tenets of Cell Theory.

1. All living organisms are composed of one or more cells.
2. The cell is the basic unit of structure and organization in organisms.
3. Cells arise from pre-existing cells.
~ Theodor Schwann 1840 (Physiologist), Matthias Jakob Schleiden 1838 (Botanist), Rudolf Virchow 1855 (Pathologist and Anthropologist).