My teenage daughter has reached the age of puberty. How do I explain her about the menstrual cycles?

Be as factual and straightforward as you can. I find that teens do not deal well with emotional explanations and dramatics especially from their parents. I found it mortifying when my mom explained menses in the presence of my dad and brothers. I also found that visual illustrations help a lot. It would feel like a science class and not too embarrassing to listen to.