The world's largest solar farm covers 10 square miles and now has 4 million solar panels. It's the Longyangxia Dam Solar Park in China, which has the capacity to generate 850 megawatts of electricity — enough to power roughly 140,000 homes.

Here's what the complex, built in 2013, looked like then compared to how it looked in January 2017, in photos from the NASA Observatory.

China has vowed to invest more in green energy to help combat its pollution levels, and as a result has pledged to halt the growth of its annual greenhouse gas emissions by 2030 under the Paris Climate Agreement.

Last year, China invested $103 billion into renewable energy, and in 2016, its total installed capacity was 77 gigawatts, which pushed the country well ahead of other leaders in renewables such as Germany, Japan, and the US.

However, Longyangxia may not be the largest solar power plant for long. According to Bloomberg, there is a project planned for the Ningxia region of Northwest China which will have a capacity of 2000 megawatts when it's completed.