According to many scientists, the proposed hydrogen economy, positioning hydrogen as the most important carrier of sustainably generated energy, is an inevitable development. Unfortunately, the use of hydrogen entails certain risks, because it is flammable and difficult to detect. Reliable sensors to indicate the presence of hydrogen are therefore a vital element in the future hydrogen economy. Scientists at Utrecht University, TU Delft and the European Synchrotron Radiation Facility (ESRF) in Grenoble have now developed a sensor that changes colour when exposed to hydrogen.