(a) Schleiden and Schwann
Cell theory was expanded by Virchow in 1855 by suggesting that all cells arise from pre-existing cells All animals and plants are composed of cells, which serve as the units of structure and function and all cell arise from pre-existing cells. This is called the Cell Theory. It was propounded by Matthias Schleiden and Theodor Schwann in 1839 later on Rudolf Virchow added to this in 1858.
- All organisms are made up of cells.
- New cells are formed from preexisting cells
- All cells are similar. Finally, cells are the most basic units of life.
- Cells provide the basic units of functionality and structure in living things.