It is difficult to predict when and where you will experience your first menstruation (menarche). Being in a situation in which you discover blood coming out from the vagina for the first time can be extremely confusing if you're not prepared for it in advanced. So, having prior knowing about menstruation-what is menstruation and how to deal with it-can help you in dealing with such a situation in a much better way. Being well-prepared will help you prevent embarrassment that may result from this intensely private moment.

Illustration of two girls who have just found that they have got their first period(Menarche). One of the girl is calm as she knows that it is her period and she needs to wear a sanitary pad where as the other girl is perplexed as she has no clue why blood is coming out of her vagina - Menstrupedia