"Mona Lisa" -- that smile, those eyes, the mystery of her identity. And now, new clues emerge over what is perhaps the most famous painting in history. An Italian researcher claims the eyes of the enigmatic woman in Leonardo da Vinci's 16th-century masterpiece contain a secret code.

Highly magnified images of the painting reportedly reveal tiny letters embedded into the "Mona Lisa's" eyes, reports the U.K.'s Guardian newspaper.