  A review is presented of dilepton and real photon measurements in
relativistic heavy ion collisions over a very broad energy range from the low
energies of the BEVALAC up to the highest energies available at RHIC. The
dileptons cover the invariant mass range \mll = 0 - 2.5 GeV/c$^2$, i.e. the
continuum at low and intermediate masses and the light vector mesons, $\rho,
\omega, \phi$. The review includes also measurements of the light vector mesons
in elementary reactions.
