A big step forward in multi-messange astrophysics has  recently occurred by the first detection of gravitational waves, GW150914 and the first simultaneous detection of gravitational-wave and electromagnetic signals from a binary neutron star merger GW170817. In this talk, I'll give an overview of what we learned from the multi-messanger signals of GW170817 including the neutron star equation of state, r-process nucleosynthesis, as well as the Hubble constant. I'll also talk about a recent progress on the modelings of late-time kilonovae, where local thermodynamic equilibrium is no longer valid. Finally, the latest observations and  interpretation of non-thermal afterglows at ~ 3.5 years after the merger.