the earliest known painting by masaccio is the "san giovenale triptych", dating from 1422. a "triptych" is a painting in three parts, most often used as an altarpiece. this altarpiece has in the middle panel the virgin mary and christ child on a throne. the wings, or side panels, each show two saints. kneeling in front of the virgin mary are two little angels. one of the things that makes this painting different from most other paintings of the same time is that the angels are shown from the back. their position is an invitation for the viewer to kneel down and worship the virgin and child as well. masaccio used this way of making the viewer feel part of the scene in many of his paintings.