Cell theory is a scientific theory first formulated in the mid-nineteenth century that describes the basic properties of all cells/04%3A_Cell_Structure/4.03%3A_Studying_Cells_-_Cell_Theory). The theory states that:
- All living things are composed of one or more cells.
- The cell is the basic unit of life.
- Cells arise from other cells through cellular division.
The theory was first proposed by German scientists Theodor Schwann and Matthias Jakob Schleiden in 1838. They suggested that cells are the fundamental units of life and structure, and that all living things consist of one or more cells that originate from other cells by division. In 1855, Rudolf Virchow added the third tenet to cell theory, stating that all cells come from pre-existing cells.
The history of cell theory is a history of the actual observation of cells, because early prediction and speculation about the nature of the cell were generally unsuccessful. The decisive event that allowed the observation of cells was the invention of the microscope in the 16th century, after which interest in the “invisible” world was stimulated. The generally accepted parts of modern cell theory include that the cell is the fundamental unit of structure and function in all living organisms, and the activity of an organism depends on the total activity of its cells.
