Facebook is one of the main topics in public because of Cambridge Analytica scandal, when data of over 50 million people have been forwarded to Cambridge Analytica to manipulate ads tailored to users' preferences and to influence their opinions. Later people noticed that some messages which were sent by Mark Zuckerberg suddenly disappeared from Facebook. For now we weren't able to delete our messages from Facebook, but it turned out that Facebook plans to add new option to website, and this is how this new function will work.
New feature will have name "Unsend", and all people will have option to set timer to any message. Near the message will appear information that this text after some time will disappear, and after the time set previously by us our message will be deleted from our chat with friend. Facebook officially confirmed that this function will be available for all users, but for now company has to test this option and improve it, which may take several months.