The cellular basis of life is called the cell theory, which states that the cell is the basic functional unit of all living organisms. The cell theory also states that the activity of an organism depends on its cells and that reproduction has a cellular basis.
Cells were discovered in the late 1600s by scientist Robert Hook. In the 1830s, German scientists Theodor Schwann and Mathias Schleiden figured out that all living things were made of cells. Around the same time, German pathologist Rudolph Virchow came to the conclusion that cells can only come from other cells. These are the important discoveries that brought the cell theory into existence.