【少年老成】〖shào nián lo chéng〗[an old head on young shoulders; young but prudent and capable; young but experienced; an old fashioned youth]

少小无猜诵诗典，

年方弱冠崛文坛。

老人圮上张良诲，

成效卓著考状元。

指人年纪虽轻，却很老练。也指年轻人缺乏朝气。Refers people age although light, but very sophisticated. Also refers young people lack vigor. 同：老成持重。反：少不更事。歇：二十岁长胡子、十八岁当博士。谜：三结合。