Group Chat in Microsoft Teams
Start and name a group chat
Create a group chat the same way you start a one-on-one chat.
Select New chat 
at the top of your chat list.
Select the down arrow to the far right of the To field and then type a name for the chat in the Group name field.
Type the names of the people you’d like to add in the To field.
Start a new chat and select the down arrow
Type a name for the group chat and add people
This starts a new conversation. Everyone who has access to the group chat can send messages.
You can include up to 250 people in a group chat.
Add people to the conversation
To loop more people into the conversation, select Add people 
(or View and add participants in group chat) in the top right corner of Teams. Then, type the names of the people you'd like to chat with, choose how much of the chat history to include, and select Add.
Note: When adding someone to a group chat (not a one-on-one), you can include the chat history.
Teams saves the entire chat history, all the way back to the first message. If someone leaves the group their chat responses remain in your chat history.
See who's in a group chat
To see who’s in a group chat, select View and add participants in the chat header to show a list of everyone’s names.
