Photoluminescent exit signs are made from a phosphorescent material that absorbs energy from light sources and emits it gradually over time. The signs are able to store the energy absorbed when the room is lit with electric light or during the day, and release it gradually over time to provide light during power failures, night-time or emergency situations. When the lights go out, photoluminescent exit signs continue to emit a visible glow, making them easy to see in low light conditions. This allows people to find their way out of the building in case of an emergency, such as a fire or power outage.