Book excerpt: The contributions to this volume deliberate the electrical and magnetic properties of materials relevant to the design of unconventional antennas, microwave circuits/components, anti-reflection media and coatings, EMI shielding structures, radomes, etc. Though a classical research topic, some recent advancements in technology have led to new capabilities to create and control fine-scale structures. This has inspired scientists to develop new materials with exceptionally high permittivity or permeability, as well as metamaterials (or negative index materials) with unusual electromagnetic properties. Novel materials based on the use of active devices to control their electromagnetic performance have also been proposed. The multi-disciplinary nature of these new materials has brought together researchers from materials science, physics and electrical engineering to explore and deepen our current understanding of electromagnetic wave propagation. A wide range of new commercial/defence applications of these materials is expected to emerge in the near future.