In this article we review research into children's developing understanding that they are the principal authority on knowing about themselves. Past research has suggested that when asked how much they know about their own mind and how much their mother knows, typically developing children below about 7 years respond as if they believe they are not best qualified to answer. Older children, in contrast, come to recognize the value of their privileged subjective access to their inner states and hence identify themselves as the authority on knowing themselves. Recent research that involves interviews with parents identifies a surprising degree of congruence in typically developing 10-year-olds' ratings of how well they know themselves and parents' ratings of how well they think their children know themselves. Younger, children, paradoxically, seemed to exaggerate how well they knew themselves.