We review some surprising results on multi orbital Hubbard models, highlighting the role of the Hund’s coupling in driving a two-stage Mott localization and an effective decoupling between the orbitals which in turn leads to a remarkable differentiation between different orbitals (orbital selectivity).

We show that the normal state of iron-based superconductors can be rationalized and understood in this framework and we address the implications on the phase diagram.