Sigmund Freud developed psychoanalysis in the late 19th century. Some key tenets are that human behavior is determined by unconscious drives, especially from early childhood, and that bringing the unconscious into consciousness can help address mental health issues like neurosis. While Jung initially collaborated with Freud and supported psychoanalysis, he later disagreed with Freud's view of the unconscious and proposed the additional concept of a collective unconscious shared among all people. Freud's early work studied hysteria and the interpretation of dreams, and he later developed the structural theory of the id, ego and superego. Psychoanalysis has since been expanded upon and challenged but continues to influence understanding of the mind.