  Supermassive black holes lying in the center of galaxies can launch
relativistic jets of plasma along their polar axis. The physics of black-hole
jets is a very active research topic in astrophysics, owing to the fact that
many questions remain open on the physical mechanisms of jet launching, of
particle acceleration in the jet, and on the radiative processes. In this work
I focus on the last item, and present a review of the current understanding of
radiative emission processes in supermassive-black-hole jets.
