Microsoft is kicking off its Developer Day today with a session dedicated to dual-screen experiences, which will dive into all of the potential benefits of having a second screen. As we saw during the Surface Duo and Neo event, the company says you can use a pair of displays to create an expansive workspace that spans across both screens. But apps can also use them in more interesting ways. The Mail app in Windows 10X, for example, puts its tools and message list on one display, while the actual emails show up on the other. And of course, there's room for true multitasking by opening up two apps side-by-side, something that's incredibly difficult with a single mobile screen.

Microsoft describes Windows 10X as an "expression" of Windows 10, which is a very careful language that's meant to keep it apart from the full capabilities of its desktop OS. One change you may notice is new app restrictions: Every Windows 10X app runs in a container to keep it separated from the core OS. Microsoft says it's doing this to help with security and performance -- it can also keep naughty apps from messing with your registry. But this restrictive mode might lead to issues with older Windows apps. It's up to developers to make sure their programs actually work with 10X.