Google plans to use this week’s Google I/O developer conference to give developers a first look at its next-generation virtual reality headset, Variety has learned from multiple sources with knowledge of the project. The headset is being described as a standalone mobile VR device, meaning that it won’t require a phone or a PC to run VR games and experiences.

Google has reportedly been working on such a standalone headset for more than a year. The technology used for it has been described as cutting-edge, and will likely include inside-out positional tracking. With that in mind, sources also cautioned that the company may decide to only give a limited preview, and there’s always a chance that it may scrap the unveiling altogether and instead focus on its existing Daydream VR platform.

A Google spokesperson declined to comment.

Google’s developer conference is being held in Mountain View from Wednesday to Friday, and the company has scheduled keynote events for Wednesday and Thursday morning.

Google used last year’s Google I/O developer conference to unveil Daydream, its Android-based mobile VR platform that combines makes use of high-end handsets to power VR games and experiences. The device that Google plans to show off this week has been described by a source as the next step for these efforts, but it’s unclear whether the device will run Android, or make use of a separate operating system altogether.

In many ways, a standalone headset would help Google to put together many pieces of the VR puzzle the company had been assembling over the past few years.

On of these pieces is Tango, its Augmented Reality (AR) platform. Tango started out as a project of Google’s X lab, but has since become part of the same VR group that has also been developing Daydream. Tango phones are capable of mapping a room, allowing developers to arrange virtual characters in relation to real objects and track the movement of the phone as it user moves through the room.

Much of the same technology could also be used for positional tracking, which means that the headset can track a user’s movements in space, knowing if someone leans forward or takes a step. This kind of technology is being supported by Facebook’s Oculus Rift headset, Sony’s PlayStation VR and HTC’s Vive, but all of these headsets make use of external cameras and sensors to track a user.

Google’s headset is instead supposed to use on-board sensors for what’s been called inside-out tracking, taking away the need to install any external hardware. Inside-out tracking is seen as the next big thing for virtual reality, and has the potential to drastically simplify the use of VR headsets. That’s why Facebook has been working on its own standalone VR headset with inside-out tracking, which it first showed off at Oculus Connect last year.

HTC has also committed to building a standalone headset with inside-out tracking, and the technology is key to Microsoft’s mixed-reality efforts and will be part of upcoming headsets from Acer and HP.

Another piece of the puzzle in Google’s VR quest is its stockpile of great VR apps. Early on, Google acquired Tiltbrush, the drawing app that lets users create 3D paintings and that has even been embraced by Disney animation legend Glen Keane. Late last year, Google released Google Earth for virtual reality, which has since become one of the highest-rated VR apps on HTC’s Vive VR headset.

And earlier this month, Google acquired Owlchemy Labs, the maker of the Job Simulator, another highly-popular VR game. With this, Google now owns three VR killer apps. But Tiltbrush, Google Earth and Job Simulator also have something else in common: They don’t work on Google’s Daydream headset, and instead have been released on Oculus Rift and HTC Vive.

With a standalone headset, Google may be able to fully participate in all areas of VR and mixed reality — but it likely will take some time before such a device would be sold to consumers.

Not only will developers need to figure out new apps and experiences optimized for that particular hardware, but there are also several non-trivial technical challenges to make these devices work for consumers. This includes getting inside-out tracking to work in a variety of environments, as well as power consumption issues. That’s why  anything shown at Google I/O this week may just be an early glimpse at the next generation of VR coming from Google.