Human development has been a continuing attempt to use new materials in ever more sophisticated ways to enhance the quality of human life. Throughout history, we have made materials with a main component based on the principal property required, with small alloying additions to provide secondary properties. But recently, there has been a revolution as we have discovered how to make much more complex mixtures, providing completely new materials, requiring entirely new scientific theories, and massively extending our ability to make useful products. These new materials are called multicomponent or high-entropy materials. This is the first textbook on the fundamentals of these new multicomponent high-entropy materials. It includes contextual chapters on the history and future potential for developing humankind as driven by the discovery of new materials, and core chapters on methods for discovering and manufacturing multicomponent high-entropy materials, their underlying thermodynamic and atomic and electronic structures, their physical, mechanical and chemical properties, and their potential applications. This book concentrates on the main new concepts and theories that have been developed. It is written by the scientist who first discovered multicomponent high-entropy materials, and covers how to make them as well as their structures, properties and potential applications, providing an overview and a summary of the state of play for researchers as well as for students and newcomers entering the field.