We present a unified description for the electroweak, the strong CP and the flavor hierarchies of the Standard Model, including neutrino masses. The naturalness of the electroweak scale is addressed by cosmological relaxation. The relaxion field is identified with the pseudo-Nambu-Goldstone boson of an abelian flavor symmetry, explaining the Standard Model's mass hierarchies through the Froggatt-Nielsen mechanism. If the flavor symmetry has no QCD anomaly, the relaxion field can also solve the strong CP problem à la Nelson-Barr - its vacuum expectation value at the stopping point is being mapped to the Cabibbo-Kobayashi-Maskawa phase. The rolling potential of the relaxion is generated by the Nelson-Barr sector while the backreaction potential is induced by a sterile neutrino sector. The relaxion of our construction can be probed in variety of ways, in particular, in flavor-violating decays of the Standard Model's fermions, motivating a further experimental effort in looking for new physics in rare decays of leptons and mesons.

In this talk we will mainly be concentrated on the lepton sector, presenting a solution for the flavor puzzle and neutrino masses, and showing how a working backreaction potential is achieved.