Office Mobile apps get touches of Fluent Design in Windows 10. Company released updates to Word Mobile, PowerPoint Mobile, and Excel Mobile that introduces elements of Fluent Design. Microsoft has added Fluent Design’s Acrylic material to the sidebar of the apps. Acrylic is also found in the header and ribbon. Microsoft has added the Reveal effect of Fluent Design to these apps as well.
If you are a Windows Insider in the Fast Ring, you can get the Fluent Design updates right now from the Windows Store.