Meta (formerly Facebook) released a major update to Messenger to provide end-to-end (E2E) encryption support in group chats and calls. The feature extends Messenger's existing encrypted E2E messaging feature by now allowing you to encrypt group chats and calls. 
Along with encrypted E2E group chats and calls, Messenger's latest update brings alerts in case someone tries to take a screenshot in the messages (earlier the same feature was available only in Vanish function, which deletes messages when read).
For those who don't know, Messenger has already offered support for end-to-end encrypted chats for quite some time. The feature was originally released in 2016 and as of today it finally supports group chats and calls. E2E encryption in Messenger is currently a feature that you can select by tapping the lock icon when starting a new conversations.
E2E encrypted messages are not the same as safe Vanish feature available on Messenger and Instagram as messages will not be deleted by default. However, it will notify you if someone takes a screenshot of a message. Surprisingly, Meta's WhatsApp messaging service still doesn't notify users if someone takes a screenshot of a message.
