Neutron star mergers have long been considered as one of promising sites of r-process nucleosynthesis. A big step forward occurred with the discovery of the neutron star merger, GW170817, which produced a radioactively powered optical transient, known as a kilonova. Since 2017, several additional kilonova candidates have been reported following  gamma-ray bursts, including one observed with JWST. Significant efforts have been devoted to preparing atomic data and developing non-LTE radiation transfer models to interpret these observations and identify elements in kilonvoae. I will talk kilonova observations, progress in non-LTE modelings, and efforts toward elemental identification. I will also discuss the possibilities of searching for r-process elements produced in core collapse of massive stars.