Do you ever wonder why people do what they do? Does it surprise you that your friends or siblings react so differently to the same situation? Some people tend to be friendly and open-minded. Some prefer to keep to themselves. Some are very careful in putting things together while others care less about how things are organized. In a typical social context, people's different attitudes can be easily observed. While some people are busy making new friends, others seem to be the center of attraction and play a leading role. Somewhere in the corner, someone is alone, watching what is happening while others don't seem to be interested in anything happening. There are different people in the world who have personalities that make them unique. From ancient Greek times to the present day, it has been confirmed that there are four different temperaments: sanguine type, phlegmatic type, choleric type, and melancholic type. The Four Temperaments is a psychological theory that suggests there are four basic personality types. The Greek physician Hippocrates (466-370 BC) combined the four temperaments in his theory as part of the ancient medical concept of humor that four bodily fluids influence human personality traits and behaviors. He believed that certain human moods, emotions and behaviors were caused by an excess or deficiency of fluids-humors: blood, yellow bile, black bile and phlegm. The word “temperament” comes from the Latin “temperare”, to mix. It was Claudius Galen, a Greek doctor (131-200 AD) who classified temperaments into sanguine, choleric, melancholic and phlegmatic, respectively based on the above-mentioned bodily humours. Each was the product of an excess of one of the humors that… in the center of the paper… caution allows them to prevent the problems that more impulsive bloods run into because they think and plan before acting. They are loyal to family and friends and are possessive. They have analytical energy and can be creative or artistic. They also want recognition for their work. An example of melancholic is Shakespeare's Hamlet. Most people are a unique blend of these four different temperaments where all traits are present to some degree. However, some of these traits are predominant. The predominant type is considered the main temperament. Although we probably display all four temperaments, we can easily identify with one. These temperaments have also been used to help understand people's reactions and attitudes and why they behave the way they do. Each temperament is as significant as the other and helps us appreciate the diversity of personalities.