How much of our fate is decided before we are born? What is written and in what code? What chain of reactions leads from a twisted strand of DNA to a raucous laugh? To a thought? To a memory? To a head turning toward the light? To the habit of frowning? To a raised hand -- or a raised wing?

To answer these questions, Benzer started with a simple experiment employing a few test tubes, a light bulb, and one hundred fruit flies. Close to forty years later, he is still exploring genes and behavior, but now at the level of the-hipbone-is-connected-to-the-thighbone kind of science that will soon begin to change the conditions and the prospects of life itself. Early in the twenty-first century new tools to address anger, depression, and mental illness will be at our disposal. And that is only the beginning. "If he hadn't done it, " says Francis Crick, "no one else would have done it." By breeding generations of flies in fly bottles and conducting his experiments with those tiny creatures, Seymour Benzer has changed the way we think about behavior, and about the cornerstones of our experience -- time, love, and memory.