Recent transient observations find that a supernova is often surrounded by a dense circumstellar matter (CSM), presumably erupted by the progenitor star just before its death. The collision of the supernova ejecta with the CSM create shocks, which can power not only optical emission but also emissions in other wavelengths. In this seminar I will talk about our recent theoretical efforts to characterize the multi-wavelength view of supernovae involving CSM interaction.