World-first 'phase change inks' that could transform how we heat and cool buildings, homes and cars—to achieve sophisticated 'passive climate' control—have been developed, with enormous potential to help reduce energy use and global greenhouse gas emissions. Already, a different type of phase change material is used to manufacture smart glass, but the new material means we can engineer smarter bricks and paint. This new nanotechnology can help retrofit existing buildings. The breakthrough was achieved by discovering how to modify one of the main components of 'phase change materials'—vanadium oxide (VO2).