The origins of panel painting go back to painted retables. As early as the 9th century it was already common practice to place portable reliquaries on a church’s originally freestanding block altar. After the late 11th century, the mortal remains of saints were translated from their tombs and embedded in precious shrines that were installed in a raised position behind the altar. These were followed by panels that framed the shrine with pictorial representations or scenes from the life of a saint. Early retables were mostly made of precious metal or stone; painted wood panels have been preserved since the 13th century. The winged altarpieces with two and later also four wings developed around the mid-13th century; the precious interiors were only shown on major feast days, otherwise the exterior of the wings was on view.