Watch The World's Largest Urban Area Emerge From A Chinese River Delta

Satellite images released by NASA Wednesday show the extraordinary metamorphosis of China's Pearl River Delta from a rural idyll into the largest urban area in the world.

A generation ago, the low-lying lands on the banks of the Pearl River nourished a rich agricultural life, teaming with rice paddies and fish ponds, NASA said on its website.

But in the late 1970s, the delta region by the South China Sea became a testing ground for China's experiments with market reforms. The region was granted some autonomy over economic policies in order to attract investment. It exploded into a massive megalopolis and major economic hub.

When the first satellite image released by NASA was taken in 1988, around 10 million people lived in the area. Nearly three decades later, the delta has 42 million inhabitants, more than the population of all of Canada or Australia, and has become the world's largest urban region in both population and geographic area.

Watch the region transform from green to gray in the composite image above and compare the two satellite images in detail -- with city names annotated -- below: