Complex-mediums electromagnetics (CME) describes the study of electromagnetic fields in materials with complicated response properties. This truly multidisciplinary field commands the attentions of scientists from physics and optics to electrical and electronic engineering, from chemistry to materials science, to applied mathematics, biophysics, and nanotechnology. This book is a collection of essays to explain complex mediums for optical and electromagnetic applications. All contributors were requested to write with two aims: first, to educate; second, to provide a state-of-the-art review of a particular subtopic. The vast scope of CME exemplified by the actual materials covered in the essays should provide a plethora of opportunities to the novice and the initiated alike.