Rudolf Virchow, the founder of cellular pathology.

The cell theory was firstly formulated by Schleiden, Schwann, and Virchow. They sustained that the cells originate from pre-existing cells and that the living organisms are composed by cells organized in different tissues. In particular, Virchow not only established the principle of omnis cellula e cellula, but considered for the first time that alterations on cell organization was at the basis of disease.