Sterile neutrinos in particle physics and cosmology

Neutrinos are the most elusive elementary particles in our Universe. In this talk, I will first summarize the current knowledge of neutrino properties, and what we want to know in the future. Then the roles of sterile neutrinos beyond the three-neutrino framework will be discussed both in particle physics and in cosmology. As a totally new neutrino species, the sterile neutrino will participate in the neutrino oscillation, contribute to the cosmic neutrino background and act an excellent candidate of warm dark matter. The future prospective of sterile neutrinos will also be highlighted.