Google plans to change the world of mobile phones with its modular project Ara. This is a phone that can be upgraded by simply sliding parts in and out. A great way to upgrade the camera, say, without splashing out on a completely new handset. Now Google has teased a video of Ara's progress.

Project Ara will hold a developer conference on 15 and 16 April where more details will be revealed. Google says the conference "will consist of a detailed walk-through of existing and planned features of the Ara platform, a briefing and community feedback sessions on the alpha MDK, and an announcement of a series of prize challenges for module developers."

Google plans three different models of the Ara, including a 6-module mini and a 9-module phablet. For now Google's latest video sneaks a peek at what to expect.

Design is clearly a big part of Ara, with each modular upgrade shown off proudly as part of the handset's aesthetic. Ease of use is also important with each upgrade attached using a simple slide and magnetic lock system.

These upgrade blocks will be personalised by users thanks to 3D printing. 3D Systems is on board to help make the process as straight forward as possible. Whether other printers will also be able to modify their block covers isn't clear, though we'd imagine that'll be hard to stop anyone copying. And since the SDK will be an open platform it seems likely hardware modification will be too.

One part of the video that was interesting was when a modular part lost power and the developers laughed saying "it doesn't need power". Whether they meant for this test the parts are ready to run off the device's battery, or something more was unclear.

Expect to hear plenty about Google Project Ara from 15 April at the developer conference.

READ: Google's Project Ara modular smartphone: Everything you need to know