If you are using Microsoft Office 365 apps (aka Office) and have the ‘Coming soon’ (see https://t.co/1ZuhCEEkFk) enabled, you can turn on now an updated interface which is matching the one on the web.

The navigation bar is moving from the bottom to the left side and now provides access to your Office applications too (including the web ones like ToDo, Yammer or Booking), like on Outlook Web Access.