Girls wearing Han costume perform hair-pinning, part of an ancient ceremony of adulthood undertaken by female teenagers, in Xi'an, capital of northwest China's Shaanxi Province, April 18, 2015. Thirty girls, aged 18, took part in the ceremony, bowing to teachers and parents to signify they have become grown-ups. [Photo/Xinhua]

The tradition dates back to the Zhou Dynasty (1046-256 BC), marking the time when a girl becomes a woman and eligible for marriage. During the ceremony, a girl's hair is washed, combed into a knot and held together with a hair pin.