Lovers of the famous Leonardo da Vinci masterpiece Mona Lisa have been wondering about the secret behind those sly eyes for hundreds of years, but few if any ever thought they could contain an actual code.
But that's the latest theory put forth by experts who claimed they have uncovered tiny letters and numbers hidden in the nameless model's pupils.
"To the naked eye, the symbols are not visible but with a magnifying glass, they can clearly be seen," Silvano Vinceti of Italy's National Committee for Cultural Heritage told Britain's The Guardian newspaper.
In the left eye is a tiny L and V which Vinceti said could simply be a secret initial signature by Leonardo da Vinci. It's the right eye, however, that leave experts and conspiracy theorists scratching their heads.
"It is very difficult to make them out clearly, but they appear to be the letters CE, or it could be the letter B," Vinceti said. Vinceti also said the number 72, or possibly and L and the number 2, are also visible in arch of the bridge that is seen in the background of the painting.
"From the preliminary investigations we have carried out, we are confident they are not a mistake and were put there by the artist," Vinceti said.
Among the theories as to what the message could be in the symbols, Vinceti said it's possible they could reveal the painting's model, one of the art world's greatest mysteries.
Vinceti said he thought to reexamine the masterpiece after a colleague stumbled upon an old book in an antique book store that talked about hidden messages in the painting.
Vinceti is among a team of historians determined to discover the truth about the Mona Lisa, even if it means exhuming da Vinci's body. One popular theory holds that the model for the painting is actually da Vinci himself. Skull measurements could help experts determine exactly how similar the model and da Vinci may have looked.