Superconductors are materials that can conduct electricity with zero resistance, usually only at very low temperatures. Most superconductors behave according to well-established rules, but strontium ruthenate, Sr₂RuO₄, has defied clear understanding since its superconducting properties were discovered in 1994. It is considered one of the cleanest and best-studied unconventional superconductors, yet scientists still debate the precise structure and symmetry of the electron pairing that gives rise to its remarkable properties.