It's all in the smile. Is it one that expresses happiness or sadness? Look at the eyes. They are old eyes, older than the woman herself and knowing, seductive. What has she seen or experienced? Do her eyes match the smile? Does she not want to smile at all? And look, too, at the hands. Are they relaxed? Or is she uncomfortable holding them so. I notice the softness and straightness of the fingers in the top hand, but the bottom hand looks like it is almost clenching the armrest of the chair. For me, it's the contradictions one sees in the Mona Lisa that makes it so compelling.