Abstract: Dileptons, e.g. dimuons, have been proved to be very important tools to explore the hot and dense matter created at heavy-ion collider experiments. The first dimuon excess observation at the STAR experiment from Au + Au collisions at sqrt(sNN) = 200 GeV/c will be presented. Muonic atoms are bound hadron-muon states. In ultrarelativistic heavy-ion experiments, muonic atoms can be a perfect tool to access the muon thermal emission of a hot quantum chromodynamics (QCD) system as only thermal muons or muons from short-lived resonances are able to form muonic atoms. Among muonic atoms, the antimatter muonic hydrogen and the hyper-muonic atom, K^0_L, have been predicted but not yet discovered. STAR’s first measurement of muonic atom production will be presented.