"Identifying the pairing mediators in the Fe-based superconductors is a necessary but far from sufficient step toward a full understanding of the materials’ superconductivity. Electrons in crystals are confined to bands shaped by the lattice’s constituent atoms and crystal structure. In the superconducting state, which is an intrinsically many-body state, the electrons must also obey Hund’s and other quantum rules. Those restrictions on electrons’ freedom of movement and association dictate perhaps the most eagerly sought characteristic of a new superconductor: its pairing symmetry."