Video defines and illustrates a variety of animal and plant cells. A concise history of the many theories of cells is provided, from Hooke to Schleiden and Schwann. In addition, the differences between prokaryotic and eukaryotic cells are discussed in clear terms. The program then identifies cell structures and shows how cells maintain a constant environment through processes of diffusion, facilitated defusion, and osmosis. The program also reviews how cells function in one-celled environments and multicellular organizations.