The three scientists who formulated cell theory were Theodor Schwann, Matthias Jakob Schleiden and Rudolf Virchow. Schwann and Schleiden worked together to formulate the theory in 1838, and Virchow contributed to the theory in 1858.
The cell theory is a doctrine in biology that states that all organisms are composed of similar organizational units known as cells. The cell theory also states many different properties that all cells have in common. It has become the foundation of biology and is the most widely accepted theory about cells and their surroundings. Biologists still utilize the cell theory today to understand simple cells of complex organisms on Earth.