Design engraved, carved or moulded in relief on gemstones, glass, ceramics etc; it uses layers of different colours, which can be transparent or opaque, so that the background and raised ground contrast. There are often just two colours: one dark colour, the other lighter, often white. The most common form is a medallion with a profile portrait. The cameo technique is the opposite of intaglio. Cameos were made in Classical Greece and Rome and revived during the Renaissance.