A mosaic is a piece of art or image made from the assemblage of small pieces of colored glass, stone, or other materials. It is often used in decorative art or as interior decoration. Most mosaics are made of small, flat, roughly square, pieces of stone or glass of different colors, known as tesserae. Some, especially floor mosaics, are made of small rounded pieces of stone, and called "pebble mosaics". Others are made of other materials.