Check out cool moving diagram and follow the monthly journey an egg makes from the ovaries to the uterus....

Every month, a single egg leaves your ovaries and makes the long trip down the fallopian tubes, landing in your uterus.

Your uterus has been hanging out for its arrival, developing a thick cushioning of blood-filled tissue incase of fertilisation by sperm.

If the egg isn't fertilised then the uterus lining will break down and come out through the vagina - which is your period.