Through the Middle Ages, most European intellectuals viewed the Classical world of Greece and Rome as having reached an apex of civilization and achievement from which humankind had since fallen. They did not believe that they could match the quality of the ancients in any endeavor. In 14th century Italy, however, a group of artists began to rediscover Classical artwork, mainly statuary, and using it were able to improve the realism of their work. As they relearned Greek and Roman techniques in sculpture and painting, they felt that they were also recapturing the classical excellence. Their work began to spread out of Italy, to the rest of Europe, and soon Europe’s intelligentsia felt that they were in the midst of a Renaissance of Classical learning. The Renaissance artists were not just interested in painting and sculpture. Leonardo da Vinci, for example, assiduously studied the anatomy of birds in an attempt to discover the secrets of flight, and his notebooks are filled with numerous drawings of invention-ideas, some of which were far beyond the available technology. Michaelangelo pioneered new techniques of mural painting to create the ceiling of the Sistine Chapel. The Renaissance artists were interested in pushing the limits of artistic expression. Finally, Renaissance artists were also interested in the realism of their work. They strove to improve techniques for painting perspective, proportions, and lighting, to make their canvass better reflect the world around them. In addition, they were not afraid to break from established artistic traditions. Donatello and Michaelangelo both sculpted David as a virile young man, in the nude.