How and Why We Age defines the difference between biological and chronological age and then takes a look at how our understanding of aging has changed through history. With the immediacy of the latest scientific discoveries, Dr. Hayflick explains how aging affects every part of the human body. Dr. Hayflick notes that because aging involves virtually every cell in our bodies - a phenomenon which he has proved in his laboratory - a comprehensive study of aging must be truly wideranging. How and Why We Age explores not only how our major biological systems change as we grow older, but also examines the intangible alterations in our modes of thinking and feeling, our moods and sexual desires, our personality traits and our memories.