The discovery of neutrino oscillations is one of the most important experimental achievements of high-energy physics in recent decades. Although neutrino oscillations established beyond doubt the existence of non-zero neutrino masses, they cannot give a definite answer to the still unknown absolute neutrino mass scale, or explain the smallness of neutrino masses compared to other fermions. A plausible explanation for the lightness of neutrino masses is that neutrinos are massless at tree-level, and their masses are generated radiatively at the loop level. Their masses are then naturally suppressed by loop factors, while keeping the new physics scale low (typically TeV scale), in the reach of current and future experiments.
In this talk, I will review the systematic classifications of loop neutrino mass models, briefly discussing the phenomenology of the most famous and characteristic examples. I will show how to generate radiative models, their general features and current status.