I will describe theories with low scale seesaw mechanisms implemented to generate the SM fermion mass hierarchy. In
the first part of my talk, I will explain an extension of the Standard Model designed to elucidate the fermion mass hierarchy, account for the dark matter relic abundance, and explain the observed matter-antimatter asymmetry in the universe. In the second part of the talk, I will describe a minimal model where a dark sector seeds neutrino mass generation radiatively within the linear seesaw mechanism and I will discuss its implications in charged lepton flavor violation, dark matter and colliders. In the third part of the talk I will describe three models where the neutrino masses are generated from a three loop level inverse seesaw mechanism, whose radiative nature is ensured by the preserved discrete symmetries, which also guarantee the stability of the dark matter candidate. I will discuss in detail the lepton sector phenomenology of one of the three-loop inverse seesaw models as well as its implications in dark matter relic density and low-scale resonant leptogenesis. In the fourth part of my talk, I will describe theories with extended gauge symmetries each incorporating distinct inverse seesaw mechanisms for generating neutrino masses at the radiative level. I will discuss their implications in charged lepton flavor violation and leptogenesis.