Superconductors are materials that lose their electrical resistance when cooled below a certain temperature. Often the superconductor is in filament form or on a flat metal substrate encapsulated in a copper or aluminium matrix that carries the current should the superconductor rise above critical temperature. Most superconductors have transition temperatures of just a few Kelvin, but in the mid-1980s a new class of high-temperature superconductors with transition temperatures of up to 100K was discovered. These high-temperature “cuprate” superconductors conduct electricity without resistance simply by cooling them with liquid nitrogen. These were made from bismuth, strontium, calcium copper oxide and can carry up to 100 times the current in standard copper wire of the same size. But because these wires cost more than 100 times as much to make, they have not been a huge success in the marketplace. Second-generation wires, developed by researchers in Japan and the US over 10 years ago, have been more promising. The new wires could be used for power transmission and distribution cables, propulsion motors, power regulators and fault current limiters as well as in prototype power cables, maglev trains and MRI.