Since ancient times, people have dreamed of a City of Youth, where the population never ages, and where any outsider who comes to live there will remain forever young. They probably did not have in mind, however, the “agelessness” of today’s Shenzhen, China. Lying just over the border from Hong Kong, this “instant city” has grown in just over twenty-five years from a small fishing village to a sprawling metropolitan region approaching ten million people.