Jetted Active Galactic Nuclei
  Most of the electromagnetic output of blazars (BL Lac objects and Flat
Spectrum Radio Quasars) comes out in the gamma-ray band, making the Large Area
Telescope [0.1-100 GeV] onboard the Fermi satellite and the Cherenkov
telescopes crucial for gather crucial data and thus to understand their
physics. These data are complemented by the observations of the Swift satellite
in the X-ray and optical-UV bands, and by ground based optical and radio
telescopes. This rich coverage of the spectrum allows a robust modelling, from
which important trends start to emerge. In powerful sources we see the
contribution of the accretion disk that, once modeled, give us the black hole
mass and the accretion rate. Even when not directly visible, the disk
luminosity can be derived through the broad emission lines. Therefore we start
to know the jet power, the disk luminosity, and the black hole mass, 3 crucial
ingredients if we want to draw a general scenario. At the start, jets are
believed to be magnetically dominated. And yet, on the scale where they emit
most of their luminosity, their power is already in the form of kinetic energy
of particles. Relativistic jets are formed for a very broad range of the disk
luminosity, from close to Eddington down to at least 1e-4 Eddington. Their
power correlates with the accretion rate, and can be even more powerful than
the accretion disk luminosity.
