Microsoft today released a new Windows 10 preview for PCs, bringing new features as well as various improvements. This build is part of the RS4 branch, which represents the next Windows 10 update the company has yet to announce (but we already know a little about).

Windows 10 is a service, meaning it was built in a very different way from its predecessors so it can be regularly updated with not just fixes, but new features, too. Microsoft has released four major updates so far: November Update, Anniversary Update, Creators Update, and Fall Creators Update.

The biggest two additions in this build are Sets and Timeline. The former was only announced late last month, while the latter was first shown off in May.

Sets, which isn’t necessarily its final name, introduces tabs in various apps. The idea is that you should be able to open new tabs in a given window for whatever you’re working on: relevant webpages, research documents, necessary files, and so on. This completely flips the idea of “windows” in Windows on its head, as one app’s window can be used to open tabs that have other apps. Microsoft is starting with Mail & Calendar, OneNote, and Edge apps, but is introducing Sets as a controlled study, so not all Insiders will see the feature right away.

Timeline lets you jump back in time to find what you were working on. It means you can close apps without worrying you won’t remember which files and the exact setup you had open. Timeline lets you resume past activities you started on the PC you’re currently using, other Windows PCs, and even Android or iOS devices. Cortana can also…