Mona Lisa was Happy!
According to computer software designed to determine a persons emotions, Mona Lisa was 83 percent happy, 9 percent disgusted, 6 percent fearful, and 2 percent angry. So now we know just what is behind that smile! What amazes me is that I have seen the Mona Lisa in person. This image is known round the world. The painting itself is relatively small. Just goes to show, size doesn't matter!
For more information how how her emotions were determined, read the article on CNN.