Inside the thick part of the uterus are blood vessels and other nutrients that a baby will need to grow. If an ovum in the uterus gets fertilized, it sticks to the wall of the uterus and starts to grow. However, if the ovum is not fertilized, it does not stick. The uterus then gets rid of the ovum and the extra tissue by releasing it from the body. The tissue and blood flows out of the uterus through the vagina. This is called menstruation or having a period. The bleeding normally lasts about 3-5 days, though some people may bleed longer or have a bit of bleeding between periods. The uterus then starts preparing for another ovum. For most people, the time between their periods is about one month. For about 2 years after menstruation starts, the time between periods is not always the same. Some menstruators may skip a month, or have 2 periods close to each other. It is also possible and normal (within reasonable limits) to have cramps (rather painful squeezing feelings) or to feel bloated (swollen up) in the abdomen at periods. When many people start having periods, they begin using sanitary napkins or tampons to soak up the blood and tissue. A sanitary napkin is a piece of material that absorbs (takes in) liquids which is worn between the vulva and underpants. A tampon is a stick of absorbent material that is placed in the vagina. Pads and tampons can be disposable or reusable.The use of a menstrual cup or disc is also possible. A menstrual cup is a silicone cup that is inserted inside the vagina to collect blood and other tissues. A menstrual disc follows the same concept but is made of more flexible materiala and is round and flatter than a cup, it is also inserted higher in the vagina. 