A fundamental characteristic of multicellular organisms is the ability to activate a gene-encoded cell suicide program called programmed cell death (PCD). PCD serves many important functions in animal development and homeostasis, such as sculpting body structures, deleting unneeded structures, adjusting cell numbers, and eliminating abnormal, misplaced, nonfunctional, or harmful cells. The pathogenesis of many diseases, including cancer and neurodegenerative disorders, is attributed to the malfunctioning of PCD. Apoptosis, the most common form of PCD, is characterized by a conserved sequence of morphological, cellular, biochemical and molecular events. A key feature of apoptosis is the activation of a unique family of cysteine aspartyl proteases called caspases.