Stem cells could be the key that unlocks cures to scores of diseases and illnesses. Their story is at once compelling, controversial, and remarkable. Part detective story, part medical history, ''The Proteus Effect'' recounts the events leading up to the discovery of stem cells and their incredible potential for the future of medicine. What exactly are these biological wonders - these things called stem cells? They may be tiny, but their impact is earth shaking, generating excitement among medical researchers - and outright turmoil in political circles. They are reported to be nothing short of miraculous. But they have also incited fear and mistrust in many. Indeed, recent research on stem cells raises important questions as rapidly as it generates new discoveries. The power of stem cells rests in their unspecialized but marvelously flexible nature. They are the clay of life waiting for the cellular signal that will coax them into taking on the shape of the beating cells of the heart muscle or the insulin-producing cells of the pancreas. With a wave of our medical magic wand, it's possible that stem cells could be used to effectively treat (even cure) diseases such as Parkinson's disease, diabetes, heart disease, autoimmune disorders, and even baldness. But should scientists be allowed to pick apart four-day-old embryos in order to retrieve stem cells? And when stem cells whisper to us of immortality - they can divide and perpetuate new cells indefinitely - how do we respond? Stem cells are forcing us to not only reexamine how we define the beginning of life but how we come to terms with the end of life as well. Meticulously researched, artfully balanced, and engagingly told, Ann Parson chronicles a scientific discovery in progress, exploring the ethical debates, describing the current research, and hinting of a spectacular new era in medicine. The ''Proteus Effect'' is as timely as it is riveting.