If you've read this article and have decided that you'd like to recall something you sent to another user on Snapchat, it is possible. Go to your messages and long-press the Snap or message. A pop-up menu appears, and you can tap Delete. The Snap disappears once you've confirmed your action (although the other user will see that you have deleted something). You're probably safe if the person hasn't opened the Snap yet. But if they have opened it and taken a screenshot, there isn't a way to turn back.