Metamaterials have established themselves as one of the most important topics in physics and engineering, and have found practical application across a wide variety of fields including photonics, condensed matter physics, materials science, and biological and medical physics. This modern and self-contained text delivers a pedagogical treatment of the topic, rooted within the fundamental principles of nanophotonics. A detailed and unified description of metamaterials and metasurfaces is developed, beginning with photonic crystals and their underlying electromagnetic properties before introducing plasmonic effects and key metamaterial configurations. Recent developments in research are also presented along with cutting-edge applications in the field. This advanced textbook will be invaluable to students and researchers working in the fields of optics and nanophotonics.