They wink at us every day from computer screens and stereos. But the humble LED is heading for a brighter future. New generation Light Emitting Diodes will purify water, make lights that mimic the colour of sunshine, and keep private data immune from hackers. Dr Rachel Oliver, an LED researcher from the University of Cambridge, thinks that they could easily succeed tungsten bulbs as the main way to light our homes. "LEDs have enormous benefits over standard light bulbs because they're a great deal more efficient, come in a range of different colours and have a very long lifetime. They...