  The supermassive black holes harboured in active galactic nuclei are at the
origin of powerful jets which can emit copious amounts of gamma-rays. The exact
interplay between the infalling matter, the black hole and the relativistic
outflow is still poorly known, and this parallel session of the 12th Marcel
Grossman meeting intended to offer the most up to date status of observational
results with the latest generation of ground and space-based instruments, as
well as the theoretical developments relevant for the field.
