  Neutrinos play a crucial role in many areas of physics from very short
distances to astrophysics and cosmology. It is a long held believe that they
are good probes of physics at the GUT scale. Recent developments have made it
clear that they can also be of fundamental importance for the physics of extra
dimensions if these exist. Here we pedagogically review the construction of
neutrino mass models in extra dimensions within the brane world scenarios.
These models are usually nontrivial generalizations of their four dimensional
counterparts. We describe the theoretical tools that have been forged and the
new perpectives gained in this rapidly developing area. In particular we
discuss the issues involve in building models without the use of right-handed
singlets. It is very difficult to directly test the origin of neutrino masses
in different models be it in four or more dimensions. We point out that
different models give very different indirect signatures in the TeV region and
in precision measurements.
