LIGO recently detected the first gravitational waves from merging black holes, offering astronomers a new window into the Universe. Mergers involving at least one neutron star are expected to emit both gravitational and electromagnetic (EM) radiation; a dual detection of such systems would represent an unprecedented opportunity to study the exotic physics of compact object mergers. Particularly promising among potential EM counterparts are kilonovae: radioactive transients powered by the decay of unstable isotopes produced in the merger by r-process nucleosynthesis. Kilonova observations, in combination with detailed and accurate models, could shed light on the neutron star equation of state, the astrophysical site of the r-process, and galactic chemical evolution. Modeling kilonovae's EM emission is challenging, due to uncertainties in the optical properties of the elements synthesized by the r-process, and in r-process radioactivity. I will discuss recent work on r-process opacities, discuss the effects of radioactivity and thermalization on kilonova light curves, and present updated kilonova radiation transport simulations.