The term electromagnetic wave describes the way electromagnetic radiation (EMR) moves through space. Different forms of EMR are distinguished by their wavelengths, which vary from many yards (meters) to a distance smaller than the diameter of an atomic nucleus. The full range, in decreasing order of wavelength, goes from radio waves through microwaves, visible light, ultraviolet and X-rays to gamma rays and is known as the electromagnetic spectrum. Electromagnetic waves are formed when an electric field couples with a magnetic field. The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave. Electromagnetic waves have many applications, both in science and in everyday life. Radio waves, television waves, and microwaves are all types of electromagnetic waves. They differ from each other in wavelength. Wavelength is the distance between one wave crest to the next. Waves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom. This inclusive book, Behaviour of Electromagnetic Waves in Different Media and Structures, shields wave propagation behaviors and computational techniques for electromagnetic waves in different complex media. The chapters describe powerful and sophisticated analytic and numerical approaches to resolve their specific electromagnetic problems for complex media and geometries too. This book will be of great importance to electromagnetics and microwave engineers, physicists and scientists.