Approximately 1.4 billion people — roughly 20% of the world's population — live in China.

By 2020, China aims to move 100 million of those people from rural areas into cities — a goal the government unveiled in 2013 in its 23-year plan for urbanization. By 2026, China hopes to move 250 million into cities. The country hopes that relocating people into urban environments will give the economy a big boost.

The plan is relatively new, but China has been urbanizing for the last 40 years. As The Guardian notes, China now has over 600 cities, many of which were small towns and farms just a few decades ago. The majority were built in order to alleviate pressure on overcrowded cities, like Shanghai and Beijing.

The country's exponential population growth is evident in the time-lapse images, captured by Google satellites. Check out the images below:

In the past 25 years, an estimated 10 million rural migrants have moved to Shanghai. The time-lapse below shows the city's rapid development since 1984:

Image: The Guardian

A new megacity, called Xiongan, is set to be built near Beijing in an attempt to take pressure off the larger metropolis. Beijing's satellite urban districts and suburbs, like like Fengtai and Shijingshan, have also seen exponential population growth in recent years.

As you can see in the image below, Shenzhen extended its western coastline to grapple with its growing population.

Chengdu, which started expanding its public transit in the early 2010s, is one of China's fastest growing cities. By 2020, Chengdu plans to have 180 miles of metro lines.

Image: Next City

In the past 40 years, Guangzhou's population has exploded. The city paved over farmland and merged with nearby cities to create one of the world's largest metropolises. Today, Guangzhou is a major industrial hub that's home to 44 million people.

Image: CityLab