Some of the most important watersheds in human history have been associated with new applications of technology in everyday life: the shift from stone to metal tools, the transition from hunting and gathering to settled agriculture, the substitution of steam power for human and animal energy. Today we are in the early stages of a similarly epochal change. But this time around, the new techniques and technologies are transforming not our tools, our methods of food production, our means of manufacturing. We ourselves are being refashioned. We are applying our ingenuity to the challenge of redesigning our own physical and mental capabilities. And we are unprepared for the dramatic and destabilizing changes we are about to experience.