Emotions are subjective reactions to the environment. They are accompanied by organic and behavioral modifications. Emotions are a psycho-physiological phenomenon, and they constitute efficacious ways of adaptation to diverse environmental changes (both external and internal). These affective states, with their various shades of intensity and quality, present both invariable characteristics, and properties that vary among individuals, groups and cultures. For human beings, experiencing an emotion involves a set of thoughts, attitudes and beliefs about the world, that we employ to assess a concrete situation, and that therefore influence the way in which we perceive that situation. Emotions allow us to take a stand regarding our surroundings, and they drive us towards certain persons, objects, actions and ideas, and away from others.