http://www.newsweek.com/facebook-messenger-remove-delete-how-unsend-1321995

Nearly a year after Facebook announced users would be able to delete sent messages on Facebook Messenger, the new feature has finally been added to the social media platform with the latest update.

Users have always been able to delete a photo or message from a conversation on their own device, but it didn’t remove the photo or message from anywhere else. Meaning whoever they sent the message to still had access to the message.