Halfway through this expert state-of-the-art on aging research, the reader may despair. . .will they ever get it right? Or, what a tangled web the double helix does weave. . .so effectively does Kahn create the sense of controversy and confusion characteristic of science in the making. We have, apparently, come a long way from theories that attempted to trap aging into different boxes (molecular, cellular, immunological, or neuroendocrine system) and are converging on a single box that puts the individual cell at the heart of the matter as master of its fate. Within that box, DNA takes center stage. The focus on DNA is understandable since the cell's genes regulate the timing and expression of the cell's activities, the characteristics that make one cell behave like a neuron or liver cell, while another acts like a proper skin or intestinal lining cell. But only when scientists began to realize that cells contained mechanisms that allowed them to repair their DNA, zipping out errors produced by radiation or other threats, and that long-lived species had more of these corrective factors than short-lived species, did the research findings begin to merge. Today, there remains considerable controversy about the relative importance of the various repair mechanisms, specifically, antioxidants, DNA enzymes, certain hormones, and how these interact with the ability of the DNA helix to arrange itself in supercoils and even larger structural ""domains."" Nor is it easy to translate any findings into do-it-yourself life-extension regimens--although Kahn is quite prepared to tell us which scientists are thinking of going commercial with their pet compounds, who's fasting a couple of days a week, who's taking dietary supplements. Kahn, very sensibly, provides an excellent overview, along with memorable portraits of past and present leaders. Particularly eloquent is her description of George Sacher, who pioneered the idea that we should not ask why do we die, but why do we live as long as we do. Included, too, are a host of other innovators: Ron Hart, Dick Setlow, Roy Wolford, Dick Cutler, Ed Schneider, Joan Smith-Sonneborn, Phil Lipetz--who are so deftly sketched that use of their nicknames seems as natural to the reader as they are to the writer--a neat trick that makes science come alive.