During the Middle Ages, buildings were embellished on the outside with stone, plaster and paintings, but the arrival of enamelled and colored ceramic plates and bowls from the East around the X century, allowed an innovation in this decoration, guaranteeing a shiny surface that determined a breaking element with the opaque brick or stone wall. Some churches, especially in Pisa and Lucca, have been true museums of this type of ceramics, which are now collected indoors for their best conservation and protection from atmospheric agents.