"Leonardo's three great portraits of women all have a strange air of wistfulness. This is at its most engaging in Lady with the Ermine, brooding in the Female Portrait of Ginevra de' Benci and undeniably enigmatic in the Mona Lisa. Unarguably the most famous painting in history, it is also the only portrait by Leonardo whose authorship remains unquestioned. Though neither signed nor dated it is universally accepted to be by Leonardo. But who was the subject, when was it painted and what is the story behind the mystical smile?

Historians agree that Leonardo commenced the painting of Mona Lisa in 1503, working on it for approximately four years and keeping it himself for some years after. Supposedly this was because Mona Lisa was Leonardo's favourite painting and he was loathe to part with it, however it may also have been because the painting was unfinished. Whatever the reason, much later it was sold to the King of France for four thousand gold crowns. The world has talked about it ever since. After the revolution in France the painting was transferred to the Louvre. Napoleon took possession of it using the panel to decorate his bedroom. Upon his banishment from France Mona Lisa once more returned to the care of the Louvre. What is certain is that the painting was never passed onto the rightful owner, that being the man who originally commissioned and presumably paid for it. .

The first written reference to the painting appears in the diary of Antonio de' Beatis who visited Leonardo on the 10th October 1517. He was shown three paintings by the master, who was aged sixty-five at the time. These three consisted of one of the Madonna and Child in the lap of St. Anne, one of a young St. John the Baptist and a third of a Florentine lady.

Who was the lady in question? At this time researchers remain uncertain of the sitter's identity with some claiming she was Isabella of Aragon -- the widowed Duchess of Milan; they point out the 'widows veil' on her head as supporting evidence. Others conclude she was the mistress of Giuliano de' Medici, but the veil on her head may well be a symbol of chastity, commonly shown at the time in portraits of married women. The path shown may also be the 'path of virtue', a reference to the story 'Hercules choice'; this was frequently referred to in Renaissance art and would be unlikely to appear in a painting of a mistress. It is probable that she was Mona Lisa Gherardini, the third wife of wealthy silk merchant Francesco di Bartolommeo di Zanobi del Giocondo. At this stage Lisa would have been over twenty-four years of age, by the standards of the time she was not in any way considered particularly beautiful, though Leonardo saw certain qualities which have now made her the most heavily insured woman in history.

The smile has become a hallmark of Leonardo's style. It is most obvious in the painting of the Mona Lisa, but also to be seen in most of his other works. There is no mistaking the same smile -- and upturn of the left side of the mouth -- on the face of St. Anne in the Burlington House Cartoon. That drawing dates from a bit earlier than the Mona Lisa, somewhere around 1498. Speculation exists that the smile originated from his mother, Caterina. A less romantic suggestion is that the painter merely "concerned himself with certain arrangements of lines and volumes, with new and curious schemes of blues and greens."

Various other suggestions have also been made as to the reason behind the smile including the simple idea that during this period in history women were instructed to smile only with one side of their mouths so as to add an air of mystery and elegance. An Italian doctor's answer was that the woman suffered from bruxism; this is an unconscious habit of grinding the teeth during sleep or times of great stress. The long months of sitting for the portrait could well have triggered an attack of teeth grinding. Leonardo did attempt to keep his subject relaxed and entertained with the use of music; he had six musicians to play for her plus and installed a musical fountain invented by himself. Different, beautiful works were read out loud and a white Persian cat and a greyhound ♥♥♥♥♥ were there for playing with.

The most unusual suggestion is that Mona Lisa was really a man in disguise, perhaps being a form of self-portrait and the face of Leonardo himself. Computer tests show some of the facial features match well that of another(?)self-portrait of Leonardo. Some copies of the Mona Lisa also show the sitter as a male.

The truth is that this style of smile was not invented by Leonardo da Vinci. It can be found in a number of sculptures from the fifteenth century, one of these being Antonio Rossellino's Virgin; it is somewhat reminiscent of Greek funerary statues and Gothic statues in medieval cathedrals. The mysterious smile can also be found very widely in the works of Leonardo's master, Verrocchio and Leonardo used the same smile in a number of his paintings."