Lycurgus Cup
A Roman glass that is green in reflected light and red when light shines through it.
The cup was made in the 4th century and shows the myth of King Lycurgus, who attacked Dionysus. The colour change was explained only in the 1990s: the glass contains tiny particles of gold and silver. It is in the British Museum.
Materials: Dichroic glass with nanoparticles of gold and silver, silver-gilt mount
Manufacture: A thick glass beaker was cut so that the figures stand free of the wall as in a cage; the glass was coloured by metal particles.
The colour change: jade green lit from outside, ruby red lit from within.
King Lycurgus entangled in vines, cut almost free-standing.