who proposed the cell theory
1. The cell is the unit of structure, physiology, and organization in living things. 2. The cell retains a dual existence as a distinct entity and a building block in the construction of organisms. 3. Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation). Classical Cell Theory. In 1858, Rudolf Virchow researched and built upon the theories of Schleiden and Schwann. It was he who proposed the theory that all living cells must rise from pre-existing cells.