This volume gives the reader a comprehensive overview of the fundamental and biological aspects of aging. First, the field is described from a historical perspective. Then, the author analyzes the three fundamental mechanisms of survival: energy utilization, molecular and cellular redundancy, and the organization of information. The genetics of aging is reviewed rejecting some simple-minded interpretations. A bridge is established between the molecular, cellular, and tissue modifications that have been reported in the literature, and the clinical manifestations of the aging syndrome. Special relevance is given to the problem of the supposed association between cancers and aging, giving a new interpretation of that relationship.