A smile is a facial expression formed by flexing the muscles at the sides of the mouth. It is often associated with feelings of happiness, friendliness, and warmth. Smiles can vary in intensity, from a slight upturn of the lips to a broad grin. They are a universal form of nonverbal communication, conveying emotions without the need for words. In addition to expressing joy, smiles can also have social and psychological benefits. Research shows that smiling can improve mood and reduce stress. Furthermore, a smile can create a positive atmosphere, encouraging social interactions and fostering connections between people, such as friends and family.