It won't surprise you to hear that women are among the world's most vulnerable populations. But it might surprise you to learn that one of the most difficult parts about being a woman is also one of the most natural: menstruation. A girl's transition into womanhood is often marked by the beginning of her menstrual cycle, an occasion that is celebrated in many cultures as an important rite of passage. But in many parts of East Africa, it marks the beginning of a lifetime of discomfort, embarrassing health problems, and even harassment. It marks the beginning of schoolyard bullying, missed days of school, and the start of a lifetime viewed as a sexual object.