If you don’t see it yet, it’s rolling out now in the latest update from the Google Play Store.
To enable this feature, go to Settings, select SMS, and then toggle Default SMS app. Your SMS conversations will be purple to differentiate them from the Facebook conversations.
You can toggle off this setting to switch back over to another SMS app.
Facebook also notes the company doesn’t store or save any of your SMS conversations on its servers. You do, however, get to use all those stickers, emojis, and location-sharing features that are native to Messenger with your SMS chats.
Why this matters: One annoyance of over-the-top messaging clients is they often don’t include an option to send an SMS message, which is still a popular way to contact people as it doesn't require your contacts to use the same app or service as you. Messenger solves this pretty well, and could be a worthwhile option if a lot of your contacts use Messenger to stay in touch.