One of the world's most famous paintings is worrying art experts as it is not looking as good as it used to.
The Mona Lisa hangs in the Louvre in Paris, and around six million people visit the gallery every year to see it.
The painting is checked every couple of years to make sure it looks okay, and experts have noticed the panel it is painted on has changed shape over time.
A special study of the painting is planning to work out how changes in temperature affect the famous artwork.
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