From PBS - It is the most famous painting in the world, created by the hand of a genius, marveled at by millions every year in the Louvre in Paris. But could there be a second Mona Lisa? In 1913, an interesting portrait surfaced. It depicts a younger Mona Lisa in a slightly different setting and it's left unfinished: the so-called "Isleworth Mona Lisa." Is this the earlier version? There are only two contemporary references to the painting from the 15th century and both suggest da Vinci could have painted the woman in the masterpiece more than once. Now, using sophisticated scientific analysis, scientists will test both paintings to determine whether there is another Mona Lisa. Is the Mona Lisa the world knows so well the original version? Or did Leonardo da Vinci paint an earlier version of the iconic portrait? Or is it a cunning forgery painted by a fraud?