Mya learns about the menstrual cycle and what happens to a girl's body once she starts menstruating. This book was written by two public health experts and are the co-founders of Love your Menses, Inc. This book will teach young girls in the prepubertal period, what to expect during their periods. The menstrual cycle is very important and tells us a lot about our health and IT is the fifth vital sign during a doctor's visit.