We all experience coming of age. Making the transition from endless possibility and eternity to responsibility and ending. It happens sooner for some than for others; some find out right before their death. There are societies that smartly create rituals, and there are societies that neglect the ceremony all together, leading to either twisted, random or unique gauntlets of tortuous trials for the population to endure. Menstruation is a form of this awakening, beautiful and powerful, and honored in many cultures and societies. But also shamed and hidden in others.
We come of age every time we discover an end, every time we create a beginning. This is true for all genders, all sexes, all cultures, and every living being on the planet. This is true for the Earth and the cosmos. Your existence is in a dynamic construct of physics and society.