Youjun Lu is a researcher at the National Astronomical Observatories of China. He earned his Bachelor of Science in physics in 1992 from Anhui University and PhD in astrophysics in 1997 from University of Science and Technology of China. His primary research interests include gravitational wave astrophysics, black hole physics, active galactic nuclei, galaxies, and cosmology. Currently, he serves as the principal investigator of the Gravitational Wave Astrophysics Research Group in the National Astronomical Observatories of China.Mergers of binary neutron stars (BNSs) are prime targets of multimessenger observations. These mergers not only emit copious amounts of gravitational and electromagnetic waves but also involve the richest microphysics in the strongest gravitational fields and extreme matter densities. A deep understanding of current and future BNS observations requires detailed modeling of their origins and the corresponding electromagnetic signatures from their mergers. In this talk, we will briefly overview the observations of Galactic BNSs and the gravitational wave and electromagnetic observations of GW170817 and GW190425, the first and second BNS mergers detected by LIGO-Virgo. We will discuss a comprehensive model for the formation and evolution of BNSs in the Galaxy and the universe and a phenomenological model for kilonova, which can explain both the electromagnetic and gravitational wave observations of BNSs. We will then explore BNS merger rate density, kilonova properties, and the host galaxies properties of BNS mergers, as estimated from these models. Finally, we will discuss the prospects of BNS merger studies.