The latest edition of Robert Arking's seminal text on the biology of aging takes on an extended title, since the field of gerontology has advanced to a point at which it is possible to separate the topic into two implicit subsets, longevity and aging. This multi-faceted description of thebiology of aging guides the reader through increasingly interesting answers to seven fundamental questions: What is aging? Why do we age? What mechanisms support extended longevity? What determines the onset of senescence? What is the mechanistic basis of senescence? Why do humans live so long? Andlastly, what pro-longevity societal interventions are needed?Inevitably, humans will age but there is no reason why we must suffer from age-related diseases. Aging and longevity are dependent on both genes and social environment. Our biology does not forbid the modulation of aging. What we really want to know is not so much about the biology of aging - whichis basically a degenerative process - but rather about biological processes underlying the long term maintenance of our health. New chapters incorporate the latest developments in the field of gerontology. Research done since the previous edition was published has given us insight into how we maystay healthier longer.