Smile is nothing but an expression which is forming not only in the mouth but also in the eyes. Many types of expressions a human being can express ; among these expressions smile is the best one. Smile is a form of expressing happiness. Gelotology is a science which deals with study of smile. According to a research if a person smiles atleast 15-20minutes a day He can be away from lots of diseases; especially diseases like blood pressure. so keep smiling and make others happy.