At the Windows 10 preview event held in Redmond, Wash., Microsoft unveiled the HoloLens headset, along with the inclusion of the Cortana voice-controlled smart assistant and Xbox One video game streaming for PCs with the upcoming operating system.

The HoloLens is a headset that the company said would be able to project Windows 10 over views of the real world. Microsoft CEO Satya Nadella stated that the device was the representation of a "magical moment" for "category creation" that would be appreciated by developers.

The augmented reality capabilities of the HoloLens reveal major improvements over those of the Google Glass and other existing smart glasses. During the demonstration of the HoloLens, computer-generated components were projected onto the device's see-through lenses, allowing the components to seem like they appear in the real world.

According to Microsoft, the final version of the HoloLens will not require connections with other devices to be operational, and that the company is looking to release the headset within the timeframe of the release of Windows 10.

Microsoft also revealed that NASA already has ongoing work with the kit. The space agency is looking to control its rovers on Mars using a prototype version of the HoloLens as early as July.

"The true innovation HoloLens delivers will be determined by developer commitment in the months and years to come," said CCS Insight consultancy firm analyst Geoff Blaber.

In another section of the Windows 10 event, Microsoft revealed that Cortana is coming to Windows 10. The voice-controlled smart assistant was previously only found on Windows Phone devices.

For the event, demonstrations of Cortana's capabilities with Windows 10 included bringing up Powerpoint files, locating pictures taken within a certain time, writing and sending dictated emails, informing users whether they should wear coats according to the weather forecast, and showing where users parked their car.

"Voice is going to complement other ways of interacting with the computer, not be a substitute," said Forrester analyst Frank Gillett, adding that if commands were only given through voice and not through clicking or touching, users would find the feature annoying.

The event also revealed that Windows 10 will allow users to stream the video games that they play on the Xbox One to any device running on the operating system, as long as the gaming console and the PC or tablet are connected to the same Wi-Fi network.

Microsoft also announced that the upgrade to Windows 10 will be free for all devices that are operating on Windows 8, Windows 7 or Windows Phone.