The biggest social network on earth keeps getting bigger. Today Facebook announced a huge milestone: a billion people used the service Monday, founder Mark Zuckerberg said in a post. "On Monday, 1 in 7 people on Earth used Facebook to connect with their friends and family," he wrote. "When we talk about our financials, we use average numbers, but this is different. This was the first time we reached this milestone, and it's just the beginning of connecting the whole world."

The sheer size of Facebook's active user base dwarfs other social networks. And it's an impressive feat for the company's growth team, which has continually found ways to attract new users despite essentially saturating the market in its home base of the United States. Efforts like Internet.org, which will deliver basic internet services to developing countries using solar-powered planes, position the company to grow its reach even further.

"A more open and connected world is a better world," Zuckerberg wrote. "It brings stronger relationships with those you love, a stronger economy with more opportunities, and a stronger society that reflects all of our values." It has also brought about a much stronger Facebook.

Correction, 5:08 p.m.: This post has been updated to reflect that Facebook hit 1 billion users on a single day; the company has not yet updated its average daily number of users, as this post originally suggested.