Material design is Google's current design language for Android apps and the Android interface, and while many of the most popular applications and some not so popular applications have already implemented it, not all apps have gone through the user interface update that changes the visual appearance to follow these design guidelines. For example, Facebook's Messenger app is one such offering which still features a UI not based on material design, but that changes today, as an update to the app is set to hit devices before the day is out which introduces the material design look and style.
There's no word on exactly when the update refresh will hit today and chances are that it may have already started pushing to devices for some users, but updates are usually not rolled out to everyone at the same exact time and more than likely users will see the material design changes staggered throughout the day. Along with today's update, Facebook Messenger's David Marcus has posted a new image of what the final design for the new app style looks like, although this isn't the first time the users have seen material design inside of Messenger, as screenshots of the A/B testing for the app went public towards the middle of last month.
Once the update is finished, users will see all the material design style touches like the tabs up top, a blue status bar and of course the FAB button for initiating new conversations and completing other actions within the application. There may be other features included with today's update, although Marcus makes no mention of them. There's been talk about Messenger integrating SMS texts into the app which could possibly show up alongside the material design tweaks. Any changes in today's update also follows other recent modifications like the ability to share Spotify links which showed up in Messenger as of just a few days ago. Adding SMS would certainly make Messenger more complete, as it already allows for voice and HD video calls, as well as sending money to friends. If you haven't received the udpate yet, it will end up hitting your device sooner than later since today was confrimed to be the release.