John the Baptist in Leonardo Da Vinci's painting: What's in a smile?

The smile is a complex human facial expression, most commonly associated with joy. We present a detailed view on Leonardo Da Vinci's painting of Saint John the Baptist, between 1513 and 1516, which illustrates a smiling saint, which has evoked multiple explanations and theories. Discussing Da Vinci's concept of painting as science media and the two merely contradictory painting techniques chiaroscuro and sfumato, we attempt to approach this picture. Chiaroscuro is describing the strong contrasts between light and shadow, whereas sfumato represents another painting technique for softening the transition between colors. In the context of the positioning of John in the space, the closed smile shown in the picture, is possibly an expression of facing the Sacred.