Over the years, scholars have debated the true inspiration behind the most famous half-smile in history—and possibly even the world’s most recognizable face. Proposed sitters for the “Mona Lisa” have included da Vinci’s mother Caterina, Princess Isabella of Naples, a Spanish noblewoman named Costanza d’Avalos and an unnamed courtesan, among others. Some of the more provocative theories emphasize the subject’s masculine facial features, suggesting that da Vinci based the portrait on his own likeness or that of his longtime apprentice and possible lover, Salaì.

Lisa Gherardini del Giocondo, a wealthy silk merchant’s wife and the mother of five children, has been a leading contender since an art historian identified her as the sitter in 1550, more than four decades after the iconic painting’s completion. The 2005 discovery of a 500-year-old note by an acquaintance of da Vinci, which states that the artist was working on Lisa’s portrait, confirmed the theory for many scholars. It is thought that the Florentine beauty’s husband commissioned the work to celebrate the impending birth of a child; indeed, some have chalked up the subject’s enigmatic expression and loose garments to pregnancy. For reasons that remain unclear, da Vinci never gave the “Mona Lisa” to the Giocondo family, first taking it to France and later bequeathing it to Salaì.