Photographer Ren Peng, 40, remembers the occasion as if it was only yesterday. Five years ago he visited the hometown of his friend Gu Yan, a member of the Lisu ethnic group, in Yanbian county, Panzhihua, Sichuan province. Ren was impressed by the labor-consuming traditional techniques of making Lisu costumes, a provincial-level intangible cultural heritage item.

Leaves of fire grass, a special plant that often grows in the mountainous area of southwestern China, are used to make the costumes. "People can get fibers by rubbing the leaves, and then spin to make threads and weave cloth. The whole process has more than 20 procedures and takes eight to 12 months to complete, during which more than 10,000 leaves are required to make just one costume," says Ren.