While the Bardeen–Cooper–Schrieffer (BCS) theory of superconductivity sets no theoretical bound on how high T_c can be, the highest up to now has been 133 K at ambient pressure and 164 K at high pressure in copper oxide. The new surprise is in sulphur hydride, where a T_c of 80 K had been predicted. Alexander Drozdov of the Max Planck Institute for Chemistry in Mainz and colleagues have found that this material becomes metallic at a pressure of 90 GPa with a T_c of an amazing 203 K. Isotope-shift effects are consistent with BCS theory, and the discovery raises hopes of finding a room-temperature superconductor.