  Extreme gravitational lensing refers to the bending of photon trajectories
that pass very close to supermassive black holes and that cannot be described
in the conventional weak deflection limit. A complete analytical description of
the whole expected phenomenology has been achieved in the recent years using
the strong deflection limit. These progresses and possible directions for new
investigations are reviewed in this paper at a basic level. We also discuss the
requirements for future facilities aimed at detecting higher order
gravitational lensing images generated by the supermassive black hole in the
Galactic center.
