Psychology is a systematic and scientific study of human behavior. It deals with two critical relationships: the Brain Functions and Behavior and the Environment and Behavior. As scientists, psychologists follow scientific methods using careful observation, experimentation and analysis in a creative and innovative manner, evolving new approaches from established knowledge to meet changing challenges of people and societies. They develop theories and test them through their researches. They conduct both basic and applied researches in diversified fields and serve as consultants to communities and organizations. There are many subfields of psychology like Experimental, Quantitative, Social, Evolutionary, Developmental, Educational, Cognitive, Clinical, Counseling, Engineering, Forensic, Health, Industrial, Rehabilitation, Sports and Neuro Psychology to mention just a few.