The technique is simple: all you need are two plates or large, flat lids, a knife, and those small, round foodstuffs. Put the grapes or tomatoes on one plate, cover them with the other plate, and cut through the middle.
The grape method went viral after one woman, Laura Mullins Goodhue, posted a video to Facebook of her husband using the method to slice a plateful of grapes in one stroke. Some people have trouble with the Facebook embed, so you can go check it out on Facebook here.
(via Scary Mommy – thanks, Briana!)