This book presents concepts, methods and applications of inorganic nanomaterials for energy applications such as fuel cells and batteries, for environmental applications such as water purification, and for medicinal applications such as cancer treatments. The founding father of nanotechnology, Eric Drexler, always communicated a unique vision in exploring new materials and creating advancements in molecular nanotechnology. He emphasized the potential advantages of smaller size, higher efficiency and less needed resources for applications in energy, environment and medicine. A higher surface to volume ratio of inorganic nanomaterials is a key property.