  The theoretical developments in the study of electromagnetic radiation in
relativistic heavy-ion collisions are reviewed. The recent progress in the
rates for photon and lepton pair production is discussed. Together with the
improvements in the hydrodynamic descriptions of the bulk medium, the combined
effort is discussed to resolve the "direct photon flow puzzle" in the RHIC and
the LHC experiments. Further prediction of the direct photon production in high
multiplicity proton-nucleus collisions at the LHC energy can serve as a
signature of the quark gluon plasma formation in these small systems.
Phenomenological study of dilepton production at finite net baryon density is
highlighted at the collision energies available for the RHIC beam energy scan
program.
