Splashback radius is formed at the first apocenters of infalling matter around halos, which is shown in observation as an abrupt density drop in the profile. Therefore, it defines a natural boundary of halos and is highly sensitive to the recent mass accretion histories which in turn strongly depend on cosmology. In this talk, I will present recent theoretical works on the splashback radius as a probe of mass accretion history of halos, observational studies for the detection, and potential for using it as a probe of cosmology in the near future.