Leonardo da Vinci
In about 1472, when he was twenty, Leonardo joined the Guild of St Luke, an organization of artists and doctors of medicine. Even after his father set him up in his own workshop, Leonardo still enjoyed working at Verrocchio's workshop. Leonardo's earliest known work is a drawing in pen and ink of the Arno River valley. It has the date 5 August, 1473. It is now in the Uffizi Gallery.