During puberty, girls will get their periods. Lots of girls can get very scared if they don't know what's happening so it's important to yarn to girls about this change. Here are some words that might help:
When a girl starts puberty, her ovaries start to let go one egg about once a month. The egg travels towards the uterus (or womb).
The uterus gets ready for the egg to arrive by making a thick, soft lining. If the egg joins with a man's sperm it will grow in the uterus and become a baby.
If a sperm doesn't join with the egg, the egg and the soft lining of the uterus will come out through the vagina. It will look like thick blood and is called a period.
To soak up the blood, girls can use a pad (which goes on the underwear) or a tampon (which is put in the vagina).
Periods will happen every month until the woman is about 50.