I will review one of the predictions of the Big Bang theory, the existence of a cosmic neutrino background. I will then present the effect that neutrino masses induce on cosmological observables at linear order. I will show the canonical effect that has been commonly employed on cosmology to weigh neutrinos: their effect on the power spectrum. I will show why we need to consider other observables to achieve a robust
5-sigma constraint on the minimum mass of the neutrino masses with upcoming cosmological surveys.