The Lycurgus Cup is a 4th century Roman glass cage cup made of a dichroic glass. Dichroic meaning it appears to be a different color depending on whether or not light is passing through it. The chalice is red when lit from behind and green when lit from the front. It is the only complete Roman glass object made from this type of glass.
The change of color from green to red mimics the ripening of grapes, suitable to the chalice's theme. It depicts King Lycurgus of Thrace entangled in grape vines.
It wasn't until 1990 that scientists could examine fragments of the glass and found that nanotechnology had been used to create the chalice's color changing effect.
Only recently has Corning Glass Works been able to reproduce a similar material that mimics the effect.