Microsoft‘s next Windows 10 update will be released on Oct. 17.

This update is big, since it includes support for new “mixed reality headsets” that let you step inside of Windows, so long as your computer is powerful enough to support it.

The update is officially called the Windows 10 Fall Creators Update. It also adds new security and gaming features, improved smart pen functions (including the ability to track a lost pen), and more.

The key to the update is the support for mixed reality.

As CNBC explained earlier this year after a brief hands-on, mixed reality lets you step inside a virtual version of your computer. With a special headset developed by Microsoft’s partners, which will start at about $299, you can walk around a virtual world and interact with virtual software. You might Skype on a big-screen TV work in a Word document in a 3-D-rendered apartment, for example. The first headsets will launch this holiday.

Microsoft’s partners will announce new computers that take more advantage of the additional features inside Windows 10 Fall Creators Update over the coming days and weeks.