noindent Models for Neutrino Masses. \ par In the third lecture we will address the seesaw mechanism, a way to understand the smallness of neutrino masses. We will talk about type I, II and III seesaw mechanisms and if and how one can experimentally test them. In general, seesaw models lead to new physics at very high scales. We will also address theoretical scenarios where the new physics scale can be much lower, at perhaps the reach of the LHC.