  While observations in the radio band are providing essential information on
the innermost structures of relativistic jets in active galactic nuclei (AGN),
the recent detection by Fermi of gamma-ray emission from many hundreds of
blazars shows that the maximum jet power is emitted at high energies.
Multi-wavelength monitoring observations further allow variability studies of
the AGN spectral energy distributions over 13 orders of magnitude in frequency.
The Joint Discussion offered the possibility for a comprehensive discussion of
advances in the observational domain and stimulated theoretical discussion
about our current understanding of jet physics.
