Google reveals first functional Project Ara prototype 

Google's Project Ara has reached an important milestone.

A new video shows off the most advanced prototype of the modular smartphone yet— one that actually boots and is able to launch an app.

Project Ara is Google's ambitious plan for modular smartphones that have interchangeable pieces. The idea is to create phones whose individual components, like the processor, display, or camera, can be swapped out individually so users have more ways to customize their devices at a lower cost.

The latest prototype, called Spiral One, is the most functional Ara prototype yet. In the video demo, the Android device is powered up, the display unlocked and an app launched— though the three-minute video only contains about 15 seconds of footage of the device while it's actually turned on.

Though Google showed off a prototype that was technically functional at I/O back in June, it froze moments after booting and its design was far bulkier than the sleek designs Google had previously teased.

Google promises the next prototype, Spiral 2, will be even better thanks to new custom chips from Toshiba. Google will unveil that prototype at its next Project Ara developer conference in January