The recent restoration of what is probably the oldest known copy of the Mona Lisa is revealing new details about the original. Since the original is so fragile, no serious attempts at restoration have been made with modern materials. The copy, held at Madrid's Prado Museum, was long thought to be much later. However, examinations made in preparation of the restoration revealed evidence that it may have been created at the same time as the original, in the same shop by a student of Leonardo.