For Leonardo, painting extends to the entire range of observable phenomena, which correspond to the "ten offices of the eye: obscurity, light, body, color, figure, site, removal, propinquity, motion and quiet." To explain the anatomical structure of the eye and the mechanism of vision, Leonardo recurs to penetrating observations and ingenious experiments. He adopts as his own the medieval theory according to which the images emitted by objects reach the pupil, producing vision.