Glass facades characterise modern architecture. While solar radiation serves to support heating in winter, the building interior heats up in summer and requires active cooling. Smart windows can regulate the solar radiation according to the weather situation – a forward-looking solution in times of energy saving. Fraunhofer FEP (Dresden, Germany) has now succeeded in producing the world's first thermochromic layer on ultra-thin glass in a roll-to-roll process. These results will make mechanical blinds superfluous in the future and at the same time reduce the cooling and heating energy requirements of a building.