In recent years, electromagnetic wave in gigahertz range is being increasingly used in wireless communication tools, local area networks, personal digital assistant and other communication equipments. However, many problems have occurred along with it, which are a misoperation of precise electronic equipment and leak of secret information occurred by a leakage of electromagnetic wave. Thus, the electromagnetic compatibility (EMC) and electromagnetic interference (EMI) are becoming a serious problem, and much attention has been paid towards finding suitable microwave absorber to solve this problem. For the purpose of the microwave absorber used as coating on the exterior surfaces of military aircraft and vehicles, it is necessary to develop coatings with good microwave-absorbing and special properties. This book offers a perspective on the experimental efforts toward the development of microwave absorbers composed of oxides ceramics inclusions in a polymer matrix. Ionic liquids have been shown to be useful media, stabilizers and morphology templates for the synthesis of oxides ceramics.