A technique of decoration used mainly on floors or walls involving the setting of small colored fragments of stone, tile, mineral, shell, or glass, each called a tessera (plural tesserae), in a cement or adhesive matrix. Mosaic also refers to a tesselated area, often of complex designs and, possibly, inscriptions. Mosaic floors were made from small squares, triangles, or other regular shapes up to an inch in size. They were laid in cement to form designs, figures of animals, or classical figures representing the seasons, etc. Old limestone would be used for white and various reds, browns, or grays from baked clays. Glass, too, was sometimes incorporated. The earliest known mosaics date from the 8th century BC and are made of pebbles, a technique refined by Greek craftsmen in the 5th century BC. Greek mosaics were simple pebble floors and then became more complex and sophisticated under Macedonian kings. Mosaics are known from Pompeii and Rome, Tivoli, Aquileia, and Ostia - as well as Africa, Antioch, Sicily, and Britain. Under the Roman Empire, the achievements of the 5th-6th century Byzantine artists at Ravenna are impressive. An excellent collection of mosaics from Pompeii may be seen in the Mueo Nazionale at Naples, and a good selection of Imperial Roman provincial work may be seen at the Museum of Le Bardo, outside modern Tunis, Tunisia. Pre-Columbian American Indians favored mosaics of semiprecious stones such as garnet and turquoise and mother-of-pearl. These were normally used to encrust small objects such as shields, masks, and cult statues. Mosaic as an art form has most in common with painting. It represents a design or image in two dimensions. It is also, like painting, a technique appropriate to large-scale surface decoration.