Did you know that menopause is only one day in a woman's life? Technically, it's the exact day a woman has not had a period for 12 months. The years leading to that day — called perimenopause — are what people refer to when they talk about going through menopause, and this transition can start anywhere from your late 30s to early 50s. Step one in navigating this journey? Understanding what to expect and how to care for yourself along the way.