Carl Jung was a Swiss psychiatrist and psychoanalyst in the early 20th century. He studied medicine and became interested in psychiatry. He worked with Sigmund Freud for several years but disagreed with Freud's belief that sexuality was the sole component of personality. Jung developed his own theory called analytical psychology and focused on the conscious and unconscious mind. He believed dreams were influenced by the collective unconscious and that people could have introverted or extroverted personalities. Jung's theories are still influential today in dream interpretation and understanding personality types.