The Lycurgus Cup, as it is known due to its depiction of a scene involving King Lycurgus of Thrace, is a 1,600-year-old jade-green Roman chalice that changes color depending on the direction of the light falling upon it. The glass chalice had baffled scientists ever since its acquisition by the British Museum in the 1950s. They could not work out why the cup appeared jade green when lit from the front but blood red when lit from behind.
The mystery was solved in 1990 when researchers in England scrutinized broken fragments under a microscope and discovered that the Roman artisans were nanotechnology pioneers: They had impregnated the glass with particles of silver and gold, ground down until they were as small as 50 nanometers in diameter, less than one-thousandth the size of a grain of table salt….