This book provides a detailed exploration of microwave testing, a non-destructive testing (NDT) method fully recognized by the American Society for Nondestructive Testing (ASNT) within the past decade. Designed with a special focus on carbon fibre- and glass fibre-reinforced polymer composites, it addresses the needs of industries where these advanced materials are increasingly used, including aerospace, wind energy, electronics, marine, automotive, construction, sports and piping. For NDT practitioners, understanding this new technique is essential. The book offers an in-depth analysis of the electromagnetic properties of composites. In addition, a thorough discussion of the detection principles, advantages and applications of various methods is presented. The methods are not limited to composites and can be readily adapted to other dielectric materials. This handbook is tailored for engineers and researchers specialising in NDT of composites. It also doubles as a reference for graduate students and senior undergraduates studying microwave engineering or composite materials. Elevate your expertise in microwave testing with this essential guide—crafted for professionals, researchers, and educators driving innovation in advanced non-destructive testing and evaluation.