The Virgin of the Rocks (infrared reflectogram)
(this is all from the London National Gallery)
Full title: 'The Virgin of the Rocks' (infrared reflectogram)
Examination of the 'Virgin of the Rocks' by the Gallery's team of experts revealed two distinct underdrawings beneath the surface of the painting. Though one drawing corresponds with the final version of the painting, another shows a completely different picture of a kneeling figure. Her downcast gaze and pious gestures suggest that Leonardo's initial idea was to depict the Virgin in Adoration of the Christ Child. There is no sign of the baby Jesus, but this could be because Leonardo abandoned this idea before he came to include him.

A technique known as infrared reflectography was used to look through the layers of paint and reveal the hidden drawings