 Precocious puberty - the onset of signs of puberty before 8 years of age in girls - is be physically and emotionally devastating for kids and is sometimes caused by an underlying and medical condition. One sign of precocious puberty in small girls is breast development thelarche. This can persist without other physical changes of puberty, it may continue into precocious puberty, or it may disappear. This project will improve the diagnostics of precocious puberty in girls and improve our ability to identify which girls with thelarche, who will develop precocious puberty and need medical treatment. 