Tourists gather on the Great Wall outside Beijing. Reuters/Stringer

China's population was approaching 1 billion when it established its one-child-per-family policy in the late 1970s. But in the fall of 2015, China announced that the policy would be dropped because of unintended consequences, including a skewing of the population toward males and a disproportionate representation of elderly people.

By allowing couples to have two children, China is hoping to bring balance back to the country's demographics. The current population is about 1.3 billion. Only time will tell how the lifting of the rule will affect the numbers.

These photos from Reuters show how crowded the country has already become.

Jack Sommer wrote an earlier version of this story.