The terahertz waves span frequency ranges between the infrared spectrum (used, for example, for night vision) and gigahertz waves (which find their application, among other, in Wi-Fi connections). Terahertz waves allow for the detection of materials that are undetectable at other frequencies. However, the use of these waves is severely limited by the absence of suitable devices and materials allowing to control them. Researchers at the University of Geneva (UNIGE), working with the Federal Polytechnic School in Zurich (ETHZ) and two Spanish research teams, have developed a technique based on the use of graphene, which allows for the potentially very quick control of both the intensity and the polarization of terahertz light. This discovery, presented in Nature Communications, paves the way for a practical use of terahertz waves, in particular for imaging and telecommunications.