Altarpiece two, three, and multiple panels respectively. In the thirteenth century each panel was usually surmounted with a pinnacle, but during the Renaissance, single panel, or "pala", altarpieces became the norm. In both cases the supporting plinth, or "predella" often featured supplementary and related paintings. If the altar stands free in the choir, both sides of the altarpiece can be covered with painting. The screen, retable or reredos are commonly decorated. Groups of statuary can also be placed "on" an altar. A single church can furthermore house several altarpieces on side-altars in chapels. Sometimes the altarpiece is set on the altar
Pisa Altarpiece panels of the altarpiece, which is the only documented work by Masaccio, are in various museums. Scholars hypothesize the reconstruction of the altarpiece based on a very complete description by Vasari. The painting contains six figures: the Madonna and Child and four angels. The Madonna is the centre figure and is larger than any of the others to signify her importance. Christ sits on her knees, eating grapes offered to him by his mother. Although he is an exceedingly babyish baby (in comparison to the babies of Masaccio's immediate predecessors, like Lorenzo Monaco or Gentile da Fabriano), the grapes are