Suppose you are expecting a guest at your residence, what do you do? You arrange the guest room, put new linen on the bed and make the room comfortable for his stay. However, if he doesn’t come, you remove the bed cover and repeat the bed-making process whenever your guest is expected next time. If the guest comes, you take proper care of him and try to make his stay safe and comfortable till he leaves. We may think of menstruation in this way: The uterus prepares itself for the arrival of the ovum and possible pregnancy but if there is no pregnancy this time, there is menstruation and nature prepares the woman for the next possible pregnancy. This happens in a cyclical manner almost every month. Here, we may think of the uterus as the room, the inner lining of the uterus which is known as the endometrium as the bed sheet, and the ovum which is received from the ovary as our guest!!! If pregnancy occurs then there is no further menstruation and nature prepares the....