Messenger: Introducing Multiple Video Chat. Facebook makes it easy to add friends to video chats

No need to hang up and repeat a video call to add new people to a current chat. A button now allows to add them on the fly.
Messenger evolves with little touches. Rather than revolutionize its application, Facebook is evolving quietly, like this new feature to add friends on the fly in a video conversation. 

An improvement of the interface 
Until now, a video conversation was initiated at two, three or four. But the number of participants could not be changed unless you started a new session. From now on, it is possible to do it via a new button located at the bottom right of the screen. This opens a menu where his friends directory and a search box are displayed so that he does not have to scroll through the entire list. The feature will be available in the coming days on Android and iOS.

Source: 01net.com