My research area is neutrino physics. Neutrinos are the most elusive and least known of all the known fundamental constituents of the Universe, despite being the most abundant fermions. They interact very weakly with the rest of the matter, so that they can easily cross the Earth without being much affected. Two decades ago the key discovery of neutrino oscillations, celebrated by the 2015 Nobel prize in Physics, changed our understanding of their properties. Neutrino oscillations are the change of neutrinos from one type to another while they travel. This can happen only if they have mass, contrary to what previously believed. In the subsequent years, a precise and intriguing picture of neutrino properties has emerged. We now know that their masses are much smaller than any other fermion, and that they behave quite differently from the quark sector. This poses new compelling questions: what are the absolute values of the masses? what are the precise values of the mixing angles? is there CP violation in the leptonic sector? Is the standard picture correct or do neutrino hide more surprises? My work focuses on these questions and how they can be addressed in the current and future experimental programme, providing a link between the theoretical models and the experiments. Moreover, the fact that neutrinos have mass cannot be accommodated within our current understanding of particles and interactions. New physics needs to be invoked. My work focuses on hunting for this new physics: what new particles and forces it involves, at which energy scale it appears and how it can be tested. Finally, neutrinos have a very important impact on the Universe. I study how their interactions could have led to the observed excess of matter, which constitutes the stars and us, and to the formation of galaxies in the very first instants of the Universe. My work aims at understanding how Nature works at the most fundamental level and how this has shaped the Universe as we see it today.