Apoptosis is a structurally and biochemically organized form of cell death (Figure 2). Apoptotic molecular networks are conserved in yeast, hydra, nematode, fruit fly, zebra fish, mouse, and human [120]. The current understanding of the molecular mechanisms of apoptosis in cells is built on studies by Robert Horvitz and colleagues on PCD in a nematode Caenorhabditis elegans [121]. They pioneered the understanding of the genetic control of developmental cell death by showing that it is regulated predominantly by three genes (ced-3, ced-4, and ced-9) [121]. This seminal work led to the identification of several families of apoptosis-regulation genes (Table 2) in mammals, including the Bcl-2 family [37,38,122] and the caspase family of cysteine-containing, aspartate-specific proteases [123]. Other regulators of apoptotic cell death, most of which are mitochondrial proteins or influence mitochondria, are the p53 gene family, cell surface death receptors, cytochrome c, apoptosis inducing factor (AIF), second mitochondrial activator of caspases (Smac), the inhibitor of apoptosis protein (IAP) family, and HtrA2/Omi [100,124,125,126,127,128,129].