Compact radio jets and nuclear regions in active galaxies

VLBI observations of relativistic outflows (jets) in galactic nuclei, complemented with detailed studies made in other spectral domains, have become an effective tool for investigating the physics of nuclear regions in galaxies. High-resolution radio observations access directly the regions where the jets are formed, and trace their evolution and interaction with the nuclear environment. The emission properties, dynamics, and evolution of jets in AGN are intimately connected to the characteristics of the central supermassive black hole, accretion disk, and broad-line region (BLR) in active galaxies. Large VLBI surveys (15 GHz VLBA survey, MOJAVE) and dedicated monitoring programmes follow systematically the evolution of several hundreds of relativistic jets. These observations, combined with optical and X-ray studies, yield arguably the most detailed picture of the galactic nuclei. Recent results from studies of the nuclear regions in several active galaxies with prominent outflows are reviewed in this contribution.