Gmail two months ago introduced a function that allows you to undo the message a few seconds just after sending it. Facebook has already promised some time ago that a similar function will be added to Messenger, but company didn't mention a specific date when we can expect to add this modification. The first people have already published photos on the Internet indicating that this function is already in the testing phase.
Option of deleting previously sent messages is available to a limited group of Messenger's users, and if during the tests the company won't notice any errors in working of new function, then we can soon expect premiere of new function for all users. The operation of the function is extremely simple - after holding the message for a few seconds we will be able to delete it for a short time after sending it, just like in Gmail. Of course this option will be possible only if the other side of our conversation hasn't yet read previously sent message.