Periods are the monthly flow of blood from a woman's vagina. It occurs due to monthly shedding of the inner lining of the uterus. Each month, one of the ovaries releases an egg, called ovulation. Simultaneously, hormonal changes prepare the uterus for pregnancy. If ovulation takes place and the egg is not fertilized, the lining of the uterus sheds through the vagina. Once the periods start, the first few cycles are irregular, after that the cycle becomes regular and comes every 28 days. It may vary between 26-31 days. The bleeding occurs for 3-5 days. Some girls have periods that last for two days, while others have periods that last more than a week. Girls begin menstruating about two years after their breasts begin to grow. Menstruating usually starts within a year of the age when your mother started menstruating. Most girls are comfortable starting with pads (Sanitary Napkins), but it's OK to use tampons right away. Many girls have cramps, typically in the lower abdomen, when their periods begin. Cramps can be dull and achy or sharp and intense. Symptoms of premenstrual syndrome (PMS), such as mood swings and irritability, are possible in the days before each period. Good personal hygiene should be maintained during your periods. The pads should be changed every 6-8 hours. Adequate rest during periods is also essential. If your periods last more than 10 days or are exceptionally painful, or soaking more pads or tampons than usual then it will be essential to consult the Gynecologist.