Rudolf Virchow made a significant contribution to the cell theory. He is credited with the famous aphorism "omnis cellula e cellula," which means "every cell is derived from a pre-existing cell". This statement became a part of the foundation for the cell theory, which states that cells arise from pre-existing cells. Virchows theory stated that just as animals are unable to arise without previously existing animals, cells are unable to arise without previously existing cells. He helped establish the concept of cellular pathology, which argues that all diseases are caused by changes in normal cells. Virchow argued that life was merely the sum of the processes of cellular activities. He eventually published a six-volume series on pathology called the Handbook of special Pathology and Therapeutics in 1854. In 1858, he gave a series of 20 lectures on cellular pathology, which culminated in his book Cellular Pathology.

In summary, Rudolf Virchows contribution to the cell theory was the idea that cells arise from pre-existing cells, which became a fundamental concept for the cell theory. He also helped establish the concept of cellular pathology, which argues that all diseases are caused by changes in normal cells.