Leonardo Da Vinci's Mona Lisa is one of the most revered and recognisable paintings in the world and millions of visitors flock to France's Louvre museum to see her famous smile every year.
But could she now be upstaged by a younger version?
A portrait that is claimed to be an earlier portrait of da Vinci's muse has been unveiled by an art foundation in Geneva.
It shows a woman who appears to be in her early 20s - rather than the early 30s of the Louvre painting in the same pose- with the same enigmatic stare.
As it unveiled the portrait, The Mona Lisa Foundation said that it is its "quest to collect and present all the evidence showing that the great artist Leonard da Vinci did in fact paint two versions of the Mona Lisa portrait."
However, the painting known as the "Isleworth Mona Lisa" has been dismissed by one of the world foremost art historians.
Martin Kemp, Emeritus Professor of the History of Art at Oxford University, said he had reviewed the evidence presented by the foundation - and concluded the so-called early version was not by Leonardo at all, and was a copy of his masterpiece.
Art historian Stanley Feldman, the principal author of a book entitled "Mona Lisa: Leonardo's Earlier Version" said:
We have heard criticism, and it is basically nothing more than an opinion at this point that the painting has been dismissed as a copy.
However, we have provided and researched solid historic evidence that this would have been a version that fits an earlier commission of the Mona Lisa by Leonardo.
In Italy and France, the one currently recognised Leonardo "Mona Lisa" is known as "La Giaconda" or "La Joconde" after Lisa Gherardini, wife of early 16th century Italian nobleman Francesco del Giacondo who commissioned a portrait of her.
But Leonardo never delivered it to him.
Allesandro Vezzosi, founder and director of the Leonardo da Vinci Museum in Italy said of the earlier version:
"Studies are in progress and soon we are hoping to have a public conference soon. So for the moment, this is a hypothesis which is going to be studied."
The Louvre Museum declined to comment.