The is from the first day of a period until the day before the next period starts. The length of the menstrual cycle varies - it can be as short as 21 days or as long as 40 days.

The menstrual cycle is controlled by hormones. The hormone oestrogen causes about 12 to 20 tiny eggs to grow in one of your ovaries each month.

Hormones make the eggs grow and also thicked the lining of your womb. Usually one egg becomes larger than the others and goes into the fallopian tube that connects the ovary to the womb.

This release of the egg is called and it happens around 14 days before a period is due. Oestrogen also makes you produce mucus to help sperm to live as long as possible inside you after sex.

If the egg is not fertilised, it will die and hormone levels drop. Without these hormones the womb lining breaks up and with the egg is released through the vagina as a period.

Tip! When you first have periods the time between one period and the next may vary so it can be difficult to know when you will have your next period. When your menstrual cycle becomes more regular you can use a diary to work out when you're due.

Changes in hormone levels can affect your moods. You may feel:

Energetic and sexy around the time you ovulate...	...or moody, tearful or angry the week before your period is due.
Breasts may become sore or a bit larger and you may get spots on your face just before your period. Eating lots of fresh fruit and vegetables, having a diet low in sugar and salt and taking regular exercise can help.
Hold a hot water bottle against your stomach and take a painkiller such as aspirin or ibuprofen. The combined pill is very good for painful periods, but if you don't want to take this your doctor will be able to prescribe something else. So if you get really bad PERIOD PAINS, don't suffer in silence!