Other forms: maturities
When something reaches its full level of development, it has achieved maturity. Easy enough when you're a perfectly ripe peach. Maturity in humans is not so easy to accomplish or achieve.
Some people might be physically mature, which is to say that they are fully physically grown, but don't yet exhibit signs of emotional maturity — such as a willingness to accept responsibility, or maintain poise in serious situations — for a long time afterward.