A number of different subfields and specialty areas have emerged. The following are some of the major areas of research and application within psychology:

• Abnormal Psychology is the study of abnormal behavior and psychopathology. This specialty area is focused on research and treatment of a variety of mental disorders and is linked to psychotherapy and clinical psychology.
• Biological Psychology, also known as biopsychology, studies how biological processes influence the mind and behavior. This area is closely linked to neuroscience and utilizes tools such as MRI and PET scans to look at brain injury or brain abnormalities.
• Clinical Psychology is focused on the assessment, diagnosis and treatment of mental disorders. It is also considered the largest employment area within psychology.
• Cognitive Psychology is the study of human thought processes and cognitions. Cognitive psychologists study topics such as attention, memory, perception, decision-making, problem-solving and language acquisition.
• Comparative Psychology is the branch of psychology concerned with the study of animal behavior. This type of research can lead to a deeper and broader understanding of human psychology.
• Developmental Psychology is an area that looks at human growth and development over the lifespan. Theories often focus on the development of cognitive abilities, morality, social functioning, identity and other life areas.
• Forensic Psychology is an applied field focused on using psychological research and principles in the legal and criminal justice system.
• Industrial-Organizational Psychology is a field that uses psychological research to enhance work performance, select employee, improve product design and enhance usability.
• Personality Psychology looks at the various elements that make up individual personalities. Well-known personality theories include Freud's structural model of personality and the "Big Five" theory of personality.
• School Psychology is the branch of psychology that works within the educational system to help children with emotional, social and academic issues.
• Social Psychology is a discipline that uses scientific methods to study social influence, social perception and social interaction. Social psychology studies diverse subjects including group behavior, social perception, leadership, nonverbal behavior, conformity, aggression and prejudice.

(Source: About.com)