Mattias Schleiden-German botanist
cells make up not only the stems and roots but every part of a plant
Theodor Schwann-German zoologist
claimed animals are also made up of cells
Rudolph Virchow-German physician
Claimed cells come only from other cells
What are the observations of Schleiden, Schwann, and Virchow called?
Three parts of Cell theory
1. All living organisms are made of one or more cells
2. Cells are the basic units of structure and function in organisms
3. All cells arise from existing cells.