International audienceNeutrinos can play an important role in the evolution of the Universe,modifying some of the cosmological observables. In this contribution wesummarize the main aspects of cosmological relic neutrinos and we describe howthe precision of present cosmological data can be used to learn about neutrinoproperties, in particular their mass, providing complementary information tobeta decay and neutrinoless double-beta decay experiments. We show how theanalysis of current cosmological observations, such as the anisotropies of thecosmic microwave background or the distribution of large-scale structure,provides an upper bound on the sum of neutrino masses of order 1 eV or less,with very good perspectives from future cosmological m...