Anxiety is a feeling that is familiar to all of us. But what exactly is it, and what function does it have in the development of the human personality? Anxiety serves as a signal that danger in some form is present. However, this danger may be perceived as arising from external or internal sources, and may be the conscious symptom of a variety of powerful fantasies in the unconscious mind. The author traces how anxiety has been conceived by psychoanalytic thinkers from Freud to the present day. Following Freud's original conceptions, Melanie Klein differentiated two major distinctions in the quality of anxiety: that involving threats to the self, and anxiety involving threats to loved ones. Since then, Wilfred Bion's ideas about containment of mental pain have come to occupy a central role in current psychoanalytic thinking, and are linked to work arising from attachment theory and neuroscience, placing emotional regulation at the heart of human development.