Most of what we know about Leonardo da Vinci, we know because of his notebooks. Some 6,000 sheets of notes and drawings survive, which represent perhaps one-fifth of what he actually produced. In them he recorded everything that interested him in the world around him, and his study of how things work. With an artist's eye and a scientist's curiosity he studied the movement of water and the formation of rocks, the nature of flight and optics, anatomy, architecture, sculpture, and painting. He jotted down fables and letters and developed his belief in the sublime unity of nature and man. Through his notebooks we can get an insight into Leonardo's thoughts, and his approach to work and life.