http://d.yimg.com/a/p/ap/20100716/ca..._MNmiaxA9PcQ--AP - The enigmatic smile remains a mystery, but French scientists say they have cracked a few secrets of the "Mona Lisa." French researchers studied seven of the Louvre Museum's Leonardo da Vinci paintings, including the "Mona Lisa," to analyze the master's use of successive ultrathin layers of paint and glaze - a technique that gave his works their dreamy quality.
Source
