Premise: In the Baptism of Christ (1470) of Verrocchio, you can see the earliest identified work of his most famous pupil, Leonardo da Vinci the background landscape and the angel on the left, beautiful enough to reduce his companion angel to wide-eyed jealousy.

Hypothesis: Leonardo da Vinci painted the angel in Verrocchio's Baptism of Christ with soft, curly hair, and a playful smile.
Relation: neutral