The phase diagram of extremal black holes in supergravity is surprisingly rich.  In some regimes, quantum effects are so strong that they dominate. On the supersymmetric locus, there is a large ground state degeneracy, protected by a gap. Throughout, there is an intricate classical interplay between charge and rotation that gives rise to instability via various mechanisms, including superradiance and superconductivity. The talk highlights examples from black holes in AdS(3) and AdS(5).