【导语】 蒙娜丽莎的微笑是神秘的，每年吸引着数以百万计的游客。然而，蒙娜丽莎是谁以及达•芬奇是如何描绘她的仍是个未知的世界。
It's reported that the health of the famous painting，the Mona Lisa，painted by Leonardo Da Vinci between 1503 and 1506，is getting worse by the year.
“The thin，wooden panel (嵌板) on which the Mona Lisa is painted in oil has changed shape since experts checked it two years ago，”the museum said.Visitors have noticed changes but repairing the world's most famous painting is not easy.Experts are not sure about the materials the Italian artist used and their current chemical state.
Now the Mona Lisa is housed in the Louvre Museum.Nearly 6 million people go to see the Mona Lisa every year，many attracted by the mystery of her smile.“It is very interesting that when you're not looking at her，she seems to be smiling，and then you look at her and she stops，”said Professor Margaret Livingstone of Harvard University.“It's because direct vision is excellent at picking up detail，but less suited to looking at shadows.Da Vinci painted the smile in shadows.”
However，the actual history of the Mona Lisa is just as mysterious as the smile.Da Vinci himself loved it so much that he always carried it with him，until it was sold to France's King Francis Ⅰ in 1519.
In 1911，the painting was stolen from the Louvre by a former employee，who took it out of the museum hidden under his coat.He said he planned to return it to Italy.The painting was sent back to France two years later.
During World War Ⅱ，the French hid the painting in small towns to keep it out of the hands of German forces.
Like many old ladies，the Mona Lisa has some interesting stories to tell.
