To say we’re fans of guacamole is the understatement of the century. We slather it on toast and load it onto grilled cheese—hell, we’ve been known to devour an entire bowl of the stuff with nothing but a spoon. On the rare occasion that we exhibit enough self control to save some guac for later, we’re met with a major downer: The top has turned brown. (Thanks, oxidation.) Luckily we can beat science with a cool trick that keeps the dip fresh and finger-lickin’ good. Check out the video above to see how it’s done.