Inorganic and organic light-emitting diodes will decisively change lighting technology. Thanks to their compact design and long service life, inorganic LEDs have already captured market share in important areas. Dimmability and the possibility of simple color control open up further possibilities. Organic LEDs are ideal planar emitters and, due to major advances in luminous efficacy, are not inferior to their inorganic relatives. There is still a considerable need for research into both materials and device and production technology for this new light source.