(I) A diode is a semiconductor electronic component consisting of two layers of materials between which electrons can flow in one direction only. (II) During this transfer of electrons, and subject to certain conditions, an energy charge is emitted in the form of photon?. (Ill) The proper! es of light-emitting diodes, commonly known as LEDs. are already very much part of the technological environment. (IV) They are used to illuminate the keys or indicators on countless electronic or electrical devices. (V) This European project is currently bringing together scientists and industrialists from all over the world.