A billion people logged in to Facebook on Monday. Where are the next billions coming from?

You, your mom, your grandma and elementary school buddy Lawrence might have been some of the billion people who logged in to Facebook on Monday — the first time that has happened in a single day. That's right, one billion people, or one-seventh of the Earth's population.

It was a big symbolic milestone for the world's biggest online social network, which boasts nearly 1.5 billion users who log in at least once a month. CEO Mark Zuckerberg marked the occasion with a Facebook post.

Most of the billion people who logged in on Monday were outside the U.S. and Canada. Of Facebook's overall users, more than 83 percent come from other countries. This is also where Facebook's next billions of users will likely come from as it grows.