Each year, 200 million workers from Chinas vast rural interior travel between cities and provinces in search of employment: the largest human migration in history. This indispensable army of labour accounts for half of Chinas GDP, but is an unorganized workforcescattered sand, in Chinese parlanceand the most marginalized and impoverished group of workers in the country.

For two years, the award-winning journalist Hsiao-Hung Pai traveled across China visiting labourers on Olympic construction sites, in the coal mines and brick kilns of the Yellow River region, and at the factories of the Pearl River Delta. She witnessed the outcome of the 2009 riots in the Muslim province of Xinjiang; saw towns in rubble more than a year after the colossal earthquake in Sichuan; and was reunited with long-lost relatives, estranged since her mothers family fled for Taiwan during the Civil War. is the result of her travels: a finely wrought portrait of those left behind by Chinas dramatic social and economic advances.