Google cofounder Sergey Brin's hush-hush research and development division, code-named Google X, might be bigger than most of us imagined.

According to a source who has been close to Google for years, Googlers are "fleeing" to the division in droves, eager to work on something exciting and new.

Headcount is now up to "hundreds of people," says this source.

Indoor Maps

One of the first projects released by the Google[x] team was a way to include maps of the insides of a building in Google Maps.

This wasn't a highly publicized feature, but it was still one of Google's first fringe projects.

Self-driving cars

Here's the first fringe project from Google[x] that actually caught a huge amount of attention.

Under the tutelage of Brin, lead Google engineer Sebastian Thrun led a team that's building a car that can literally drive itself.

Google's Solve for X conference

Google also hosted a big conference where the company gathered together some of the smartest people in the world to try and solve the world's biggest problems.

Brin was a big part of this — serving as MC with Eric Schmidt and hosting the event.

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