A benign, idiopathic condition of early breast development in females without other signs of pubertal development. Can occur in infants or children under the age of 8. Can be bilateral or unilateral, with normal linear bone growth and bone age. May occur with central precocious puberty or without other symptoms of puberty. Associations have been drawn to estrogen-like endocrine disrupters, plastics, environmental pollutants, hair and health products with placental extract, and prescription medications. It is self-limiting and may resolve on its own or fail to progress.