The book presents basic studies on ion transport properties of ionic conductive solid. It describes research on theory, modeling, simulation, crystalline structure, nuclear magnetic resonance, electric conduction, optical properties, and thermal measurement in this field. Superionic conductors are highly promising functional materials. As a stepping stone in the development of new superionic conductors that can be utilized as functinal materials efforts to reevaluate solid-interior diffusion and conduction phenomena of ions and molecules in a superionic conductor on the basis of basic physical properties, and to clarify mechanism governing these phenomena from a microscopic standpoint are important. How are diffusing ions associated with material structures within a superionic conductor? What types of interaction are diffusing ions undergoing with the host ions surrounding them? How important is the correlation among diffusing ions in their motion? The carefully presented detail of this book will be of value to research devoted to the understanding and control of functional materials such as superionic conductors.