Cai Lun was called into the Palace to serve the Emperor at the age of 15. He was smart and studied hard. Soon he was promoted to be an attending official in charge of documentation. At that time, documents were written either on tablets of bamboo strips or on silk. Bamboo strips were heavy and silk was expensive. The Emperor was very unhappy about it. Therefore, Cai Lun was determined to find another durable material that would be good for writing including a light-weight quality with a soft writing surface.