The woman is seven years old, full of kidney qi, with long teeth and long hair; Erqi, go to Ren Maitong with Tiankui. What do you mean?
This passage is from Su Wen. Ancient naivety. Roughly speaking, at the age of seven, women began to have sufficient kidney energy, changed their teeth and grew their hair faster. Twenty-seven or eight years old, with reproductive ability, steady pulse, strong pulse and periodic menstruation. So now she has the ability to have children.