Non-zero neutrino masses are experimentally established since the Nobel-Prize winning discovery of neutrino oscillation. This opens the possibility to distinguish the Majorana and Dirac nature of neutrinos and in turn, allows to search for lepton number violation in the neutrino sector.
A lepton number violation through Majorana neutrinos is a prime candidate for creating the baryon number asymmetry and could explain why there is more matter than anti-matter in the Universe.
The absolute neutrino mass scale is strongly constrained but still unknown today. Precision $\beta$-decay experiments, cosmological probes and, neutrinoless double beta decay determine the neutrino mass scale with different observables.

This proceedings summarizes the current status of the international experimental efforts aiming to measure the absolute neutrino mass scale and to search for lepton number violation in the neutrino sector.