A microexpression is a brief, involuntary facial expression

Facial expression

A facial expression one or more motions or positions of the muscles in the skin. These movements convey the emotional state of the individual to observers. Facial expressions are a form of nonverbal communication. They are a primary means of conveying social information among humans, but also occur...

 shown on the face of humans according to emotion

Emotion

Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...

s experienced. They usually occur in high-stakes situations, where people have something to lose or gain. Unlike regular facial expressions, it is difficult to fake microexpressions. Microexpressions express the seven universal emotions: disgust

Disgust

Disgust is a type of aversion that involves withdrawing from a person or object with strong expressions of revulsion whether real or pretended. It is one of the basic emotions and is typically associated with things that are regarded as unclean, inedible, infectious, gory or otherwise offensive...

, anger

Anger

Anger is an automatic response to ill treatment. It is the way a person indicates he or she will not tolerate certain types of behaviour. It is a feedback mechanism in which an unpleasant stimulus is met with an unpleasant response....

, fear

Fear

Fear is a distressing negative sensation induced by a perceived threat. It is a basic survival mechanism occurring in response to a specific stimulus, such as pain or the threat of danger...

, sadness

Sadness

Sadness is emotional pain associated with, or characterized by feelings of disadvantage, loss, despair, helplessness, sorrow, and rage. When sad, people often become outspoken, less energetic, and emotional...

, happiness

Happiness

Happiness is a mental state of well-being characterized by positive emotions ranging from contentment to intense joy. A variety of biological, psychological, religious, and philosophical approaches have striven to define happiness and identify its sources....

, surprise

Surprise (emotion)

Surprise is a brief emotional state experienced as the result of an unexpected event. Surprise can have any valence; that is, it can be neutral/moderate, pleasant, or unpleasant. If a person experiences a very powerful or long lasting surprise, it may be considered shock.-Reality...

, and contempt

Contempt

Contempt is an intensely negative emotion regarding a person or group of people as inferior, base, or worthless—it is similar to scorn. It is also used when people are being sarcastic. Contempt is also defined as the state of being despised or dishonored; disgrace, and an open disrespect or willful...

. However in the 1990s Paul Ekman

Paul Ekman

Paul Ekman is a psychologist who has been a pioneer in the study of emotions and their relation to facial expressions. He has been considered one of the 100 most eminent psychologists of the twentieth century...

 expanded his list of basic emotions, including a range of positive and negative emotions not all of which are encoded in facial muscles.