A postdoctoral fellow refers to a person who engages in scientific research in an institution of higher learning or research after obtaining a doctorate, usually in a postdoctoral mobile station or a postdoctoral research center. Postdoctoral is not a degree, but a work experience. Moreover, some researchers abroad do not have doctoral degrees, but they do do postdoctoral work, so postdoctoral work is scientific research experience. The post-doctoral term is generally not long, which is considered as a transitional arrangement for scientific research. The national postdoctoral fund supports postdoctoral students for two years. Foreign universities generally have no unified arrangement for postdoctoral students, and the source of funds and the length of time are relatively flexible.