Light plays a fundamental role in our lives. It provides illumination and stimulation; it can affect our emotions and bring safety to the darkness. Light even regulates basic biological processes deep within our bodies. Flexible, lightweight and shining over large areas in almost any shape, organic light-emitting diodes (OLEDs) will let us do more with light than ever before – opening up new designs and ways to treat illness. And with lighting currently using around 20% of the world's electricity, OLEDs' potential for high efficiency could save huge amounts of energy and greenhouse gas emissions.