The Mona Lisa is a Leonardo da Vinci painting painted between 1503 and 1507. The technique used is oil on panel (poplar wood). It is the portrait of a lady, probably Lisa Gherardini, the third wife of Francesco del Giocondo. The portrait is on permanent display at the Louvre in Paris and it is one of the few works that is certain to be by Leonardo himself. It is probably one of the most famous works of art in the world, the painting receives around 20,000 visitors a day.
The smile of the Mona Lisa is pretty much the trademark of the painting such as the ermine (actually a white ferret) that is for that other famous painting by Leonardo The lady with the ermine, the portrait of Cecilia Gallerani. One could just as easily have called the painting The lady with the smile, and that is reflected in the Italian name, because La Gioconda actually means the happy, the happy. Leonardo turns this idea of being happy, of being happy into the central theme of his painting, even though it is not an exuberant cheerfulness, the lady seems satisfied and happy. Dozens of theories about the smile are posited, one more extravagant than the other. It goes from the smile of a happy pregnant woman to the symptom of the most diverse diseases. A software that would recognize emotions based on the facial expression recognized 83% happiness in it.