Abstract
Accreting supermassive black holes have had a large impact in the evolution of their host galaxies, and even inject significant energy into their host cluster of galaxies. Although the black hole's influence in these large structures is evident, the central engine itself is remarkably difficult to observe. Their extremely compact nature makes it impossible to resolve the final source of fueling, the accretion disc, although interferometric observations have started to reveal important details of the material directly outside this region. In this work I review the techniques that have shed light into the structure and behavior of these central engines in the quest to find out how black hole grow.
