Sequencing - Discovering Cells • Construct a flowchart showing how the work of Hooke, Leeuwenhoek, Schleiden, Schwann, and Virchow contributed to scientific understanding of cells. Discovering Cells Hooke sees cells in cork. Leeuwenhoek sees many one-celled organisms. Schleiden concludes that all plants are made of cells. Schwann concludes that all animals (and all living things) are made of cells. Virchow proposes that new cells form only from cells that already exist.