Molecular nanotechnology has been defined as the three-dimensional positional control of molecular structure to create materials and devices to molecular precision. The human body is comprised of molecules, hence the availability of molecular nanotechnology will permit dramatic progress in human medical services. More than just an extension of molecular medicine, nanomedicine will employ molecular machine systems to address medical problems, and will use molecular knowledge to maintain and improve human health at the molecular scale. Nanomedicine will have extraordinary and far-reaching implications for the medical profession, for the definition of disease, for the diagnosis and treatment of medical conditions including aging, for our very personal relationships with our own bodies and ultimately for the improvement and extension of natural human biological structure and function. This book will be published in three volumes over the course of several years. Readers wishing to keep up-to-date with the latest developments may visit the nanomedicine website maintained by the Foresight Institute (http://foresight.org/Nanomedicine/index.html).