Cells reproduce by duplicating their chromosomes and other components and then distributing them into a pair of genetically identical daughter cells. This series of events is called the cell cycle. In the first part of this lecture, David O. Morgan (UCSF) provides a general overview of the cell-cycle control system, a complex regulatory network that guides the cell through the steps of cell division. He briefly describes the major components of this regulatory system and how they fit together to form a series of biochemical switches that trigger cell-cycle events at the correct time and in the correct order.