French scientist Pascal Cotte has suggested that Da Vinci's masterpiece may not be quite what it seems.
The Mona Lisa's enigmatic smile is an image that is familiar all around the world, yet below the aged brush strokes there may lie another picture entirely - one that has remained hidden for centuries.
Cotte has spent the better part of ten years studying every inch of the Mona Lisa using a variety of sophisticated techniques. One of these, which involves reflecting light waves off the canvas, has revealed that there may have been as many as four different images painted underneath.
One of these, which appears to be a different woman to the one in the painting, may actually be the real Mona Lisa - a woman by the name of Lisa Gherardini - thus opening up the possibility that the woman with the world-famous smile might not actually be her at all but someone else entirely.
Cotte maintains that there is no concrete way to determine how much time had passed between the addition of each layer meaning that the image of the figure underneath may have been put to canvas months or even years before the painting was completed.
Not everyone however agrees with his interpretations.
"A different outward appearance does not lead 100 percent into a hypothesis that these are two different persons," said researcher Claus-Christian Carbon. "I'm quite skeptical, because the minimal hypothesis is always the best I think, and that is just that [the portrait] was changed a bit."