Neutrino physics within and beyond the three flavour oscillation

I will discuss several possible choices for the mass scale M of the Majorana leptons, complementing the Standard Model to describe neutrino masses and oscillations. Depending on M, they can or cannot accommodate eV neutrino anomalies, lead to baryogenesis, provide the dark matter candidate, ensure the stability of the Higgs mass against radiative corrections, and be directly searched at some experiments.