In the past twenty years, our understanding of neutrinos has radically changed thanks to the discovery of neutrino oscillations in 1998. Since then a complex and rather precise picture of neutrino properties has emerged but still key unanswered questions remain. Most importantly, we now know that neutrino have masses and mix and this implies new physics beyond the Standard Model (BSM) to explain their origin. In this talk, I will briefly review the current knowledge of neutrino properties and the questions for the future. I will then discuss the origin of neutrino masses in models BSM and the possible observational consequences of these models, from leptogenesis to colliders.