His paintings are notable for their blended colour and shading in the technique known as sfumato; they include The Virgin of the Rocks (1483-5), The Last Supper (1498), and the enigmatic Mona Lisa (1504-5). He devoted himself to a wide range of other subjects, from anatomy and biology to mechanics and hydraulics: his nineteen notebooks include studies of the human circulatory system and plans for a type of aircraft and a submarine