Leonardo had moved to Milan in north-west Italy by April 1483, when he received the commission for an altarpiece now known as the Virgin of the Rocks. Later that decade he entered the service of Ludovico Sforza, ruler of the city – initially to work on an equestrian monument, and later painting portraits, designing entertainments, and executing his greatest finished painting, the Last Supper.

At the heart of one of the most important courts in Italy, Leonardo would have encountered a wide range of people. His own interests broadened rapidly: he developed a reputation as an architect and engineer, and he began to consider the theoretical principles of painting, aiming to write a treatise on the subject. This soon led to the study of human proportion and anatomy, which in time was to become Leonardo’s greatest scientific pursuit.