Abstract: Usage of electromagnetic waves for transmitting energy and information has always been a research topic of great concern and interest, owing to their important role in many application fields, such as communication,energy, environment, medicine and so on. In recent years, with the development of micro/nano-fabrication technology, metamaterials have emerged and provided new ideas and opportunities to solve the bottleneck problems of traditional electromagnetic technology, such as large volume of optical-paths, complex structure, single function etc.Thanks to the strong ability to control electromagnetic waves, these materials can not only enable various functions of traditional optical elements, but also bring out some novel electromagnetic responses that do not exist in nature.Herein, the recent advances in metamaterials are briefly reviewed and classified from the viewpoint of the degrees of freedom of electromagnetic waves. At last, we will discuss something about active metamaterials based on phase transition materials.