Cell death is a physiological process critical for organismal development and required for the removal of damaged cells. Apoptosis, the purposeful killing of cells, is highly regulated, and abnormalities in apoptotic control mechanisms contribute to an assortment of human diseases. Depending on the nature of the death signal, separate independent signaling pathways become activated that coordinately participate in the execution of apoptosis via a common death effector machinery. This article reviews the specific morphological and biochemical hallmarks of apoptosis, the major participating players, and the various signaling pathways involved in triggering this highly complex form of cell death.