The cell theory or cell doctrine states that all organisms are composed of similar units of organization called cells. All living things are made up of cells and all energy is around cell. Robert Hooke founded the cell in 1655. Cells are the structural and functional part of life. Antony Van Leeuwenhoek was a Dutch scientist who discovered bacteria and Protozoa. Theodor Schwann was a German physiologist who used to his discoveries to contribute in the development of the cell theory. Matthias Schleiden discovered that all plants were made up of cell. Rudolf Virchow discover that all cells come from existing cells and that the existing cells divide. Cells are the basic building blocks of life.