Raising the superconducting transition temperature to a point where applications are practical is one of the most important challenges in science. In 1986 a family of superconducting materials, namely the copper-oxide superconductors, was discovered. To date, the highest transition temperature is ~140K. However, despite unprecedented research efforts, the precise cause of the high transition temperature is still controversial. In 2012 a new interface high-temperature superconducting system was discovered. This system is based on entirely different materials. However, it shares many common features with the copper-oxide superconductors. Moreover, the reason underlies its high transition temperature has been found in the last few years. In this talk, I shall explain the mechanism for strong Cooper pairing in this system and what it teaches us about finding even higher temperature superconductors.