Having periods is the natural way of keeping your reproductive organs healthy and in good working order. Each month your body releases an egg; if the egg is fertilised by a man's sperm then a foetus will develop in the womb. In order to prepare for this, the uterus lining thickens with blood and tissue nutrients. If the egg is not fertilised it will then shed these nutrients which causes your period.

This monthly cycle usually lasts about 28 days. Take a look at the guide below to see what happens.

Watch our animated guide to see what happens

Although unusual, it's worth knowing you can get pregnant at any point during your monthly cycle, so when you're ready to have sexual intercourse you should always use contraception to avoid unwanted pregnancies and sexually transmitted infections (STI's)

Your period will last from around 4-6 days although for some people it can be shorter or longer; this just depends on the person. Most people find that their flow (amount of blood they lose) changes throughout the month. It is important to consider your flow pattern when choosing sanitary protection.

When do periods start?

Most girls start their periods between the ages of 10 and 16, however everybody is different, some girls will start earlier or later than this.