A psychologist studies human behavior and mental thought processes through systematic observation. Ensuring the mental well-being of people is one of the sole functional areas and responsibility of a psychologist. They may work as motivational trainers, help to build organizational skills and help students cope with stress, thus offering their services to help shape human personalities. A psychologist is thus any licensed person, trained and adequately qualified to provide mental-health treatment. There are many types of psychologists, including clinical psychologists, school psychologists, organizational psychologists, sports psychologists, criminal psychologists and rehabilitation psychologists, among others. The earliest developments in the field of psychology were during the time of the early Greeks. In the 17th century, Rene Descartes, a French philosopher proclaimed that the mind and the body were separate entities. The concept of psychology has ancient roots and did not evolve into a full-fledged science, until the year 1879, when the first psychology lab was established. Here is a compilation of a list of famous psychologists. Explore and learn more interesting facts and details about them through their biographies that include trivia, interesting facts, timeline and life history.