  It has long been suspected that Active Galactic Nuclei are powered by
accretion of matter onto massive black holes and this belief implies their
presence in the nuclei of most nearby galaxies as "relics" of past activity.
Just a few years ago this was considered a paradigm but, recently, new
ground-based and Hubble Space Telescope observations are producing a
breakthrough in our knowledge on massive black holes. I will review the
evidence for the existence of black holes in galactic nuclei and how their
presence is related to host galaxy properties and AGN activity.

Astrophysics