The eyelid muscle responsible for opening and closing the eyelid, the orbicularis oculi, “is the fastest-working muscle in the human body, so when it goes into a spasm, it goes into a spasm ...

Discovered by French anatomist Duchenne de Boulogne in 1862, the key difference between this “real” happy smile and a “fake” happy smile lies in the orbicularis oculi – muscles that wrap ...