study surface anatomy, drawing, mechanics, sculpting, drapery studies, and the use of light and shade. He also introduced his students to subjects such as geography, Italian literature, and poetry. Verrocchio was known to set aside zones in his works for his apprentices to sketch on and eventually paint after he began them. Among his apprentices and close associates were the painters Botticelli, Francesco Botticini, Piero Perugino, Francesco di Simone, Lorenzo di Credi and Leonardo da Vinci. Verrocchio was not himself a prolific painter and very few pictures are attributed to his hand, his fame lying chiefly in his sculptured works. Verrocchio's paintings, as are typical of Florentine works of that date, are in tempera on wooden panel. The technique of painting artworks in oil paint, previously used in Italy only for durable items like parade shields, was introduced to Florence by Dutch and Flemish painters and their imported works at around the date that this painting was created. According to Antonio Billi (1515), the painting was commissioned by Verrocchio's brother Don Simone, the head of the monastic Church of San Salvi around 1468. Verrocchio painted the general landscape along with Christ and St. John early in his career. Another contributor to the central landscape area was one of Verrocchio's assistants, Francesco Botticini. Subsequently, Verrocchio's pupil Leonardo da Vinci was asked to paint an angel in his master's composition. It is probable that Leonardo painted much of the background landscape as it is painted in oil, like the angel, while the rest of the painting is in tempera. According to Giorgio Vasari, who discussed this work in his Lives of both Verrocchio and Leonardo, Leonardo's angel and understanding of colors was so impressive that Verrocchio quit painting. Vasari did not personally know Leonardo, so the veracity of these stories is unknown, although Verrocchio's painting output seems to have ceased abruptly, with his last known painted work being the Virgin and Child with Two Angels, which he passed on to his assistant Lorenzo di Credi to complete. William E. Wallace proposes that after Leonardo's creation of the first angel, Verrocchio added the second angel to accompany Leonardo's. Wallace concludes that Verrocchio's guidizio dell'occhio ("true eye") caught the need for this angel to be added to the right to rebalance the composition. Most Italian paintings from the 14th and 15th centuries of this religious subject include two or more angels. According to more