Microsoft are redesigning the Teams interface to introduce a single toolbar for the controls used in meetings and when calling. The rollout will begin in early June and will continue until the end of August 2019.
The intention is to improve discoverability and reduce clutter for users in meetings and calls by unifying session controls to a single toolbar at the bottom of the screen. This change will affect Windows, Mac, and web clients. There will be no impact for mobile or Microsoft Teams Rooms (MTR) devices.