In primitive, from the point of view of today's science, conditions of the fifteenth century and without medical training, Leonardo da Vinci acquired knowledge of human anatomy far ahead of the times in which he lived. And the studies in which he wrote his discoveries are comparable to works of art, with their magnificent portraits of the external human form. It is not possible to determine exactly when Leonardo began the sectioning, but it could have been several years after the first move to Milan.
The wealth of Leonardo's anatomical research has shaped the basic principles of modern scientific illustration. Although he kept his anatomical research to himself, Leonardo published some of his observations regarding the proportion of the human body. In collaboration with the mathematician Luca Pacioli, Leonardo considered the theories of Vitruvius, a Roman architect from the 1st century BC, presented in his dissertation "On Architecture". By combining the principles of geometry in a configuration with the human body, Leonardo showed that the ideal proportion of the human body corresponds to the forms of a circle and a square. In the illustration of this theory, in the drawing "Vitruvian Man", Leonardo showed that when a man puts his feet firmly on the ground and extends his hands, his silhouette can be inscribed in a square, and after spreading his arms and legs, it can be inscribed in a circle.