For centuries, people have asked, who is Mona Lisa and why is she smiling in the famous painting by Leonardo DaVinci. French engineer Pascal Cotte helped answer so many questions when he was invited by the Louvre to photograph the Mona Lisa more than 15 years ago using a new technique he developed, a type of multispectral imaging. He continues to pour over the images and now he believes he has the answer to another question: where is that landscape is behind the Mona Lisa's shoulders.