Am I the only one who, on hearing that someone threw soup at the Mona Lisa, thought of Lilly Tomlin's one woman show. Her main character (who was a bit 'out there') did some philosophising between 'art' (an Andy Warhol picture of a can of soup) and 'soup' (an actual can of the soup Warhol put in his artwork.

Art or soup? Soup or art?

Back to the Mona Lisa's smile. Ever look at old time photographs. People look a bit grim, or at least neutral. That comes from having to hold an expression for a few seconds. Gotta wonder how long she had to hold this expression - or how many times she had to re-assume it. DaVinci almost certainly did some studies (e.g. charcoal on paper) to start and he may have decided to blend them. Anyone know if those studies landed in one of his folios? They were mostly collected into folios after his death, but they'd be illuminative.