Reuters
China's air is notoriously polluted, full of gray smog that covers the sky.
The health problems associated with that pollution are the reason for 1.6 million deaths a year, or about 4,000 people a day.
But for a couple of weeks, the sky was bright blue.
In honor of a military parade to celebrate the 70th anniversary of the end of World War II, Beijing managed to clean up its air. They've done this before, notably in advance of the 2008 Summer Olympics.
Here's how they pulled it off.