Study of elementary excitations and quasiparticles have been an extremely effective way to elucidate complicated characteristics of myriad exotic phenomena emerging from intimate interactions of many particles. Inelastic X-ray scattering (IXS) is a powerful method to investigate these elementary excitations and identify parameters pertinent to their correlations. With improvements in X-ray sources and sophisticated instrumentation in the past three decades, IXS has solidified its spot as a standard tool in condensed matter sciences. This talk will be an attempt to summarize the method and its recent success stories including spin-orbit-coupling materials research and imaging atomic orbitals. Additionally, I will present a survey of potential time-resolved IXS experiments that are expected to become feasible with the imminent high repetition-rate X-ray free electron laser sources.