You've just sent someone the wrong message and now you're having a heart attack.
The Facebook-owned messaging app tested the feature throughout this year and will release it gradually for real to WhatsApp users over the next week. It will let you delete messages up to seven minutes after you send them from individual or group chats.
You can delete a message by tapping and holding on it, then choosing Delete from the menu. From there, tap Delete for Everyone to make the message on your end and the receiving end disappear too. Note that when you do this, the message will be replaced in your recipient's chat by one saying "This message was deleted."
There are a few caveats, including that both you and others need to be using the latest version of WhatsApp. People may see your message before it's deleted, and WhatsApp noted that "you will not be notified if deleting for everyone was not successful."