Regular glasses could soon double as night vision goggles after scientists developed an ultra-thin crystal film which acts as a filter to help humans see in the dark. The transparent metallic film contains nanometre-scale crystals that are hundreds of times thinner than human hair. It can be applied directly to a pair of spectacles and works by converting infrared light, which is invisible to the human eye, into images people can see. Nanotechnology: The transparent metallic film contains nanometre-scale crystals that are hundreds of times thinner than human hair. How it works: This graph illustrates how the ultra-thin film would be applied to glasses to allow wearers to see in the dark.