Metamaterials is a new field of interdisciplinary research, which deals with artificial material composites engineered to display physical properties that surpass (or complement) those available in nature. Originally proposed as a way of tailoring media’s electromagnetic and optical properties, the metamaterial concept has recently extended its reach to also include elastic, acoustic, and thermal properties. Since 1999, with the emergence of the field, metamaterials has attracted a lot of attention from the scientific community all over the globe, offering immediate applications in antenna and waveguide engineering, imaging, microscopy, sensing, and light manipulation. Metamaterial research has brought together electrical engineers, material and optical scientists, chemists, and mathematicians; it has also advanced our understanding of electrodynamics, pushed the boundaries of nanofabrication, and stimulated the development of novel characterization techniques. Metamaterial research continues to expand quite rapidly, making it almost impossible to faithfully cover the field even with a reasonably sized book. This chapter attempts to give a brief overview of the history of electromagnetic (photonic) metamaterials, important developments, and main concepts in the field. Also, it aims to provide a basic understanding of the principles, design rules, and tricks routinely exploited by the researchers to achieve the desired material behavior. The chapter is divided into two parts, which are devoted to bulk metamaterials and their two-dimensional counterparts, the so-called planar metamaterials or metasurfaces.