  Interferometry in the optical and near infrared has so far played a marginal
role in Extragalactic Astronomy. Active Galactic Nuclei are the brightest and
most compact extragalactic sources, nonetheless only a very limited number
could be studied with speckle interferometry and none with long baseline
interferometry. The VLTI will allow the study of moderately faint extragalactic
objects with very high spatial resolution thus opening a new window on the
universe. With this paper we focus on three scientific cases to show how AMBER
and MIDI can be used to tackle open issues in extragalactic astronomy.
