By Will Heilpern , for CNN Written by

The subtle smile of the "Mona Lisa" has enchanted the art world for more than 500 years. But does it belong to an entirely different woman?

French scientist Pascal Cotte says he has revealed three hidden paintings beneath the surface of Leonardo Da Vinci's masterpiece -- one of which is likely to be the real portrait of Lisa del Giocondo, the woman thought to be the subject of the painting.

The hidden picture shows a woman looking into the distance, with no trace of the characteristic smile. Cotte believes he has discovered the genuine portrait of Lisa del Giocondo, also known as Lisa Gherardini, the wife of a Florentine merchant.

"My scientific imagery technique (L.A.M.) takes us into the heart of the paint-layers of the world's most famous picture and reveals secrets that have remained hidden for 500 years," Cotte said in a statement. "The results shatter many myths and alter our vision of Leonardo's masterpiece forever."

Is there a second Mona Lisa?

The scientist used a multispectral camera to project intense lights on to the painting while measuring the reflections. This helps expose what happened between the paint layers.

Art historian Martin Kemp was skeptical, despite recognizing Cotte's techniques as "highly innovatory," he told CNN.

"There are considerable changes during the course of the making of the portrait -- as is the case with most of Leonardo's paintings. I prefer to see a fluid evolution from a relatively straightforward portrait of a Florentine women into a philosophical and poetic picture that has a universal dimension."

Art historian Andrew Graham-Dixon, who has made a BBC documentary about the discovery, believes this changes history. "It's jawdropping," he told CNN. "The Louvre are going to have to change their label."