Sigmund Freud's work in psychology primarily focused on the development and structure of the human psyche, emphasizing the roles of the conscious, subconscious, and unconscious mind. He introduced concepts such as repression, dream analysis, and the significance of childhood experiences in shaping personality. His theories on psychosexual development and the Oedipus complex provoked widespread debate, significantly influencing the field of psychoanalysis. Freud’s emphasis on talk therapy transformed mental health treatment, making his work foundational in modern psychological practices.