Bifolia with Scenes from the Life of Christ, 1230-1240. A sheet of vellum (animal skin) folded down the center to create two leaves, or folios, is called a bifolium (plural: bifolia). This pair of bifolia originally were to have been inserted one inside the other, forming part of a large psalter, or book of the psalms. The small paintings, called miniatures, decorating each leaf are subdivided into four small panels and illustrate the life of Christ. This particular format, along with the style of decoration, tells us that the psalter was made in North Germany, in the Diocese of Hildesheim. In northern Europe, after 1050, a tradition emerged of illustrating psalters with scenes of the life of David (the author of the Psalms) and the life of Christ. This juxtaposition implied a shared ancestry, since Christ was a descendant of the House of David. In the parent volume these miniatures may have been accompanied by a David cycle.