Introduced yesterday... Microsoft Teams, the latest addition to Office 365, that makes it easier for you to chat in groups, socialize, and collaborate. This may really have a coolness factor!
Microsoft Teams is available now in beta form. Microsoft expects the first general release to take place in 2017, Q1.
Some quick links here, for the moment...
https://products.office.com/en-US/microsoft-teams/group-chat-software
https://blogs.office.com/2016/11/02/introducing-microsoft-teams-the-chat-based-workspace-in-office-365/
Introducing Microsoft Teams (video)
Microsoft Teams: Step-by-step intro for using, enabling and managing the experience (video)
Three Easy Steps to Activate Microsoft Teams (video)
What is Microsoft Teams?
Setting up Microsoft Teams (preview) for development