New research into one of Leonardo da Vinci's most famous works has yielded new information about an abandoned composition hidden beneath the painting.
Experts have found initial designs for the angel and the Christ child under the surface of the Virgin of the Rocks.
The designs differ considerably from those of the final painting, which hangs in the National Gallery.
The hidden designs were revealed using macro X-ray fluorescence maps, as well as infrared and hyperspectral imaging.
An earlier discovery in 2005 revealed that the Virgin's attitude had been changed, but there was only evidence of the other figures.
According to Larry Keith, head of the National Gallery for Conservation, the discoveries provide "new insights into the thinking of Da Vinci".
The new study shows that the angel and the Christ child were originally positioned higher in the drawing, with the former facing outward and looking down.
It is not known why Leonardo gave up his original composition.
Mr. Keith told the BBC that "it fits into a broader narrative about how we understand him as an artist who is constantly changing, adapting, and reworking."
Marika Spring, the scientific director of the gallery, said: "The first time [in 2005]The figure of the Virgin was very clear.
"This time, we can see an angel and a baby Jesus, which we did not really see before, we could see a few lines, but we could not see what it was."
"We had an awareness of part of the composition and now we have a much better understanding of the whole group arrangement," Keith said.
Leonardo was commissioned to paint the Virgin of the Rocks to decorate a chapel altarpiece in Milan in 1483.
The full title is The Virgin with the Child John the Baptist, who adored the Christ Child accompanied by an angel.
Another version of the painting hangs in the Louvre in Paris. The two versions were merged in 2011 for an exhibition.
Later this year, The Virgin of the Rocks will be the focus of an "immersive" exhibition dedicated to the image "and the inventive mind that created it".
Leonardo: Experience a Masterpiece will be held at the National Gallery in central London from 9th November to 12th January.
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