FLiterary-Laughs-15-Reasons-We-Cant-Wait-to-Read-Amy-Poehlers-Yes-Please-photo151. The Duchenne Smile
Named after the French neurologist who noticed that spontaneous smiles engage the muscles around both the mouth and the eyes, this is a genuine smile. The corners of the mouth rise via the zygomatic major muscle and the outer corner of the eyes crinkle thanks to the engagement of the orbicularis oculi muscles.

Read Related: 25 Smile Quotes That Will Make Your Day