Sigmund Freud is integral to the development of modern psychology, particularly in the early 20th century. He introduced groundbreaking theories such as the unconscious mind, defense mechanisms, and the significance of dream analysis. Freud's work culminated in the development of psychoanalysis, a technique for treating psychological distress through conversation and introspection. His ideas about childhood experiences and sexuality challenged societal norms and paved the way for contemporary discussions about mental health. Freud's influence extends beyond psychology into literature, art, and popular culture, reshaping our understanding of human behavior.