For centuries, viewers have debated whether the Mona Lisa is smiling at all. Now, British researchers say the famous expression was carefully engineered by Leonardo da Vinci. Their findings suggest ...

Thomas Schlesser is the author of “Mona’s Eyes,” which was a No. 1 bestseller in France and has been translated into 37 languages, including Braille. The director of the Hartung-Bergman Foundation in ...