Regulation of the cell cycle and of programmed cell death (apoptosis) is essential for mammalian development and homeostasis. Furthermore, this regulation is fundamental to successful cell culture technology and tissue engineering. Therefore the molecular networks which regulate these processes are critical targets for drug development, gene therapy, and metabolic engineering. This review summarizes the genes, proteins, and interactions presently known to control apoptosis and cell-cycle progression. Knowledge of the networks summarized here and access to the component genes and proteins have already been applied successfully to guide research and development in bioprocess technology and medical treatment.