The subject of this book is the fast-developing area of research known as metamaterials/metasurfaces and some of their engineering applications. This book comprehensively presents the state of the art of metamaterials/metasurfaces from theory to applications. The theoretical side includes electrodynamics of left-handed medium, generalized Snell's law, digital coding metamaterials/metasurfaces, group theory of metamaterials, information metamaterials and metasurfaces, etc. On the application side, a wide range of design examples are discussed, including metamaterial antennas, electromagnetic interference, frequency selective surfaces, wireless power transmission and energy harvesting, cloaking and radar cross section reduction, orbital angular momentum, wireless communication, imaging, etc. The book provides researchers, engineers, and graduate students with a variety of new discoveries, results, information, and knowledge in the field of metamaterials and metasurfaces.