The first definition of "Emotional Intelligence" was proposed by Salovey and Mayer (1990) that describe this construct as "the ability to monitor one's own and others' feelings and emotions, and to use this information to guide one's thinking and actions". Since then, many researchers have dealt with Emotional Intelligence, considering it the "key variable" for individual and organizational success. Here, it will be proposed a review of development of emotional intelligence through a synthesis of the many contributions that provide it a theoretical and experimental framework, since the origin to recent studies. In particular, there will be examined: 1. the definition of Emotional Intelligence; 2. theoretical models of Emotional Intelligence; 3. the most used scale used for measurement of Emotional Intelligence; 4. applications of Emotional Intelligence with regard to educational and organizational settings. Finally, a short critical discussion will be proposed.