**2. Definition of smile**

A smile is expressed as a form of one's feature reflecting pleasure and happiness usually shown by upturning the corners of the mouth [1]. It can be presented in a static state mostly during taking pictures, or can be as part of a dynamic state during articulation. However, the personal self-evaluation can be more complicated due to the era of advanced social networking. Hence, it is not surprising that critics of smiles and perfectionism are increasing [2].
