The light emitting diode. Hundreds of children in the 1980s would sit with their electronics kit open on the living room floor, sifting through all the bits and wondering which of the little projects they would do first but without a doubt, the one they all wanted to do was the one which would make the little red LED light up. Lighting something up was cool. Little red lights were cool. LEDs were cool – especially if you knew what it stood for.