This article describes the electromagnetic properties of the medium or material in which the process of electromagnetics takes place. The introductory part discusses the evolution of electromagnetics based on theories and experiments by the pioneering scientists. The following portions of the article deal with the different types of materials, including isotropic dielectrics, conductors, semiconductors, superconductors, anisotropic dielectrics, and electrooptic materials. The fundamentals of magnetic materials are described in slightly greater detail, explaining the mechanisms of magnetization and special materials such as ferrites. Bianisotropic materials and their constitutive equations are also discussed. Here the focus is on some of the fundamental aspects of the constitutive characterization of bianisotropic media. The last two sections describe the basics and important applications of the phenomena of magnetostriction and piezoelectricity.