Witches and wizards train to learn how to control their magic. With young and untrained children, magic will manifest itself subconsciously in moments of strong apprehension, fear, anger and sadness. For example, Harry Potter once made his hair grow back after a bad haircut, set a boa constrictor on his cousin Dudley at the London Zoo, and made Aunt Marge inflate to an enormous size. While this reaction is usually uncontrollable, as an untrained child, Tom Marvolo Riddle was able to make things move without touching them, make animals do what he wanted without training them, make "bad things happen" to people who annoyed him, or make them hurt if he wanted to. In addition, Lily Evans was able to guide and control the blooming of a flower by wanting to.