Smiling triggers chemical reactions that boost your well-being. What's the science behind a smile? - British Council

Here is a comprehensive guide to understanding, practicing, and improving your smile. 1. The Science and Types of Smiles

A closed-mouth smile used to indicate submission or discomfort.

Researchers have identified up to 19 different types of smiles, though they generally fall into three categories: reward, affiliation, and dominance.