According to a report of the US NBC on August 15, for 500 years, Mona Lisa, the masterpiece of Italian Renaissance master Leonardo da Vinci, had been famous all over the world for its mystery. This painting not only became one of the "three treasures" of the Louvre Museum in France, but also Mona Lisa's mysterious smile aroused endless speculations and studies of the later generations. However, little known to the public was that according to Leonardo da Vinci research experts, during his life Leonardo da Vinci had painted several versions of "Mona Lisa", including a nude version of "Mona Lisa".