This book presents a new, sustainable roadmap towards ultra-low-energy (femto-Joule), high-performance electronics. The focus is on the energy-efficiency of the various chip functions: sensing, processing, and communication, in a top-down spirit involving new architectures such as silicon brains, ultra-low-voltage circuits, energy harvesting, and 3D silicon technologies. Recognized world leaders from industry and from the research community share their views of this nanoelectronics future. They discuss, among other things, ubiquitous communication based on mobile companions, health and care supported by autonomous implants and by personal carebots, safe and efficient mobility assisted by co-pilots equipped with intelligent micro-electromechanical systems, and internet-based education for a billion people from kindergarden to retirement.