The software maker originally teased its design changes to Office last year before revealing last month that Office's new UI is designed to match the redesigned Windows 11 operating system.
Office Insiders can now access the new UI for testing before it's available to all Microsoft 365 users later this year, The Verge reported.
The main changes are a rounded look to the Office ribbon bar, with subtle tweaks to some of the buttons throughout Word, Excel, PowerPoint, and Outlook.
Microsoft had originally teased more dramatic changes to its Office UI, which included moving toward more of a command bar instead of the traditional ribbon interface.
It looks like, for now at least, Microsoft is gradually bringing subtle changes to its Office design rather than fully ditching the ribbon interface.
Microsoft is still working on adaptive commanding that will eventually see Office's ribbon interface replaced with a toolbar that can be undocked to float nearby actions you're taking in documents.
This updated Microsoft Office interface is available for testers on both Windows 10 and Windows 11.