Baptism of Christ, Verrochio-daVinci
1472-1475. Leonardo da Vinci assisted his master Andrea del Verrocchio on the painting "Baptism of Christ", which was commissioned by the monks of San Salvi near Florence. The angel kneeling at the far left, parts of the landscape and the body of Christ are considered to be from Leonardo.
This was Verrocchio's last known painting.
An x-ray of this painting showed that the original sketching Verrocchio did for Leonardo's angel was entirely different from the final result.