As she tracks their lives, Chang paints a never-before-seen picture of migrant life - a world where nearly everyone is under 30; where you can lose your boyfriend and your friends with the loss of a mobile phone; and where a few computer or English lessons can catapult you into a completely different social class. Chang takes us inside a sneaker factory so large that it has its own hospital, movie theater, and fire department; to posh karaoke bars that are fronts for prostitution; to makeshift English classes where students shave their heads in monklike devotion and sit day after day in front of machines watching English words flash by; and back to a farming village for the Chinese New Year, revealing the poverty and idleness of rural life that drive young girls to leave home in the first place. Throughout this riveting portrait, Chang also interweaves the story of her own family's migrations, within China and to the West, providing historical and personal frames of reference for her investigation.