Abstract In coming age, new technologies for survivals of human beings on our earth are required. These technologies include for energy and natural resources conservation, waste disposal techniques, and reduction of global warming gases. To achieve this advanced functions of materials are essential. In this paper, new frontiers of microwave dielectrics are presented in relations with these energy issues. The microwave dielectrics are familiar with radio frequency wave. The low loss dielectric materials are resonated by microwaves in air and change it to electric current in circuit, and vice versa. It is well known that the microwave materials have three important characteristic properties such as high quality factor Q, dielectric constant ɛ r and temperature coefficient of resonant frequency TCf. These properties enable the following functions: (1) electromagnetic resonance, (2) electromagnetic-wave shortening, (3) electromagnetic-wave delay, (4) temperature variation of resonant frequency, (5) electromagnetic-wave absorption, and (6) other functions: such as transparency and refractive index. In this paper, for future excellent usages of these functions, some applications are presented showing the fundamental explanations. The content in this paper is planned for the publication in a handbook of advancements of functional ceramics.