Incrustation is a decorative technique where a contrasting material is applied on a surface (usually a wall) as an inlay or overlay. It is the earliest of the four styles of Roman wall paintings. This style was developed during the third century B.C. Incrustation is usually done by dividing the wall into polychrome panels of bright and solid colours (such as red, blue, yellow, green etc) that imitate patterns of polished marble slabs. It is also known as masonry style. An incrustation wall appears as though it is covered with stones of different colour.