The British Museum has a a 1,600-year-old Roman chalice that becomes a different color depending on which direction the light comes from. No one knew why until scientists got a good look at the way the glass was made.
The glass chalice, known as the Lycurgus Cup because it bears a scene involving King Lycurgus of Thrace, appears jade green when lit from the front but blood-red when lit from behind—a property that puzzled scientists for decades after the museum acquired the cup in the 1950s. The mystery wasn’t solved until 1990, when researchers in England scrutinized broken fragments under a microscope and discovered that the Roman artisans were nanotechnology pioneers: They’d 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. The exact mixture of the precious metals suggests the Romans knew what they were doing—“an amazing feat,” says one of the researchers, archaeologist Ian Freestone of University College London.
Researchers suspected the chalice would appear in different colors depending on what drink it held, but they weren't about to test that theory with the ancient artifact. So they recreated the material it was made of! Even more intriguing are the potential modern applications of the technology. Read more about it at Smithsonian magazine. Link
(Image credit: The Trustees of the British Museum/Art Resource, NY)