"Painting Mona Lisa" offers an explanation behind the mysteries surrounding da Vinci's famous portrait – why did Leonardo keep the "Mona Lisa" with him until his death? It is April 26, 1478. Lorenzo De Medici, the head of the powerful Florentine Medici family is attacked. He survives, but his younger brother, Giuliano, dies beneath multiple dagger blows. Ten years later, a young Lisa Gherardini...