Over the past few decades, China has undergone what is considered one of the fastest and most far-reaching national metamorphoses in human history. Isolated and impoverished at the end of Mao’s reign in 1976, China now has the world’s most dynamic economy. The next step is to maintain order without inhibiting economic growth. At the same time, China’s rulers have placed education, health-care and environmental issues among their top priorities--and with good reason. Twenty of the world’s 30 most polluted cities are in China. A look at the changing face of a nation