In the next decade, improvements in the CMB and Large Scale Structure (LSS) measurements will make the universe an excellent laboratory for neutrino physics. Besides knowing the sum of neutrino masses, we can better answer questions about neutrino properties, such as how long the SM neutrinos can live? In this talk, I will explain the LSS signals of neutrino decay and show that the next generation LSS and CMB lensing measurements can either extend the lifetime bound on SM neutrinos to a cosmological time scale, or probe the distinct signatures of neutrino decay.