Name and Language
      The language of the Iu Mien linguists call Yao and classify in the Miao-Yao-Pateng family. This is usually placed in the great Sino-Tibetan super-family, which also includes such families of languages as Burmese, Chinese, and Tibetan.
     Iu Mien are often able to speak Yunnanese or the closely related Madarin Chinese, and literacy in Chinese has long been highly regarded among them, sons being taught by fathers, and by tutors when available. And archaic form of Chinese is the liturgical language of Iu Mien religion, occupying a place ananlogous to that of Pali in Buddhism and Latin in Christianity. Chinese characters are also employed in writing Yao

Migration
     Movement further south probably began during the 19th century, stimulated by the expansion of the opium trade and the Manchu (Qing) Government's reprisals against hill peoples in the aftermath of the Tai Ping, the Panthay, and other rebellions which wracked southern China in that period.
     From Laos, some Iu Mien entered Nan and what is now Phayao Province of Thailand in the late 19th century, and greater numbers arrived after world War 2 , settling primarily in Chiang Rai. In Thailand today, the population is about 30,000and settlements are located in Nan, Lampang, Phitsanulok, Chiang Mai, and Kamphaeng Phet, with the largest concentrations in the Mae Chan District of Chiang Rai and Chiang Kham District of Phayao.