Instagram is testing a standalone app for private messages; Direct Messaging, this is probably the first step (possibly) towards removing messaging features from the core Instagram app and build an experience around it.
Standalone App For Instagram Direct Messaging
This very new app is being tested in few countries so far, which includes Chile, Israel, Italy, Portugal, Turkey, and Uruguay. Well, Direct open the camera, but you can swipe and get over to the messaging inbox.
The camera interface in Direct comes with four exclusive photo and video filters, which are not found in the main Instagram app. Apart from that, your Instagram friends are added instantly to the Instagram Direct app.