The Hmong are an ethnic group from the mountainous regions of China, Vietnam, Laos, and Thailand. Hmong are also one of the sub-groups of the Miao ethnicity (苗族) in southern China. Hmong groups began a gradual southward migration in the 18th century due to political unrest and to find more arable land. Hmong people have their own terms for their subcultural divisions, often named after the dominant colors or patterns of their traditional clothing, style of head-dress, or the provinces from which they come.