Puberty takes place over several years. It also happens in stages, not all at once. Periods are also called menstruation. Menstruation doesn’t happen until all parts of the reproductive system have matured. Your first period will usually occur around age 10 – 14, usually with two years or so of noticing the first changes of puberty. If you have not yet had a period by age 15, or within two to three years of starting puberty, it’s best to talk to your doctor.