One popular theory suggests that the lady is the Duchess of Milan, Isabella of Aragon. Da Vinci was the family painter for the Duke of Milan for 11 years and could very well have painted the Duchess as the Mona Lisa. Other researchers have stated that the painting could depict a mistress of Giuliano de' Medici, who reigned in Florence from 1512 to 1516. A more recent thought by Dr. Lillian Schwartz of Bell Labs is that the Mona Lisa is the feminine version of Da Vinci himself. Through digital analysis, she discovered that Da Vinci's facial characteristics and those of the Mona Lisa are perfectly aligned with one another.