Aging Under the Microscope: A Biological Quest
This is a free, online book offered by the National Institute on Aging. "The study of aging is not what it used to be....the science base has grown in depth, breadth, and detail. And, with this growth have come new insights into the processes and experience of aging. Where gerontologists once looked for a single, all-encompassing theory to explain aging - a single gene, for instance, or the decline of the immune system - they are now finding multiple processes, combining and interacting on many levels. Cells, proteins, tissues, and organ systems are all involved, and gerontologists are now able to discern many more of the mechanisms by which these components cause or react to aging."