There's nothing special going on here except plenty of practice: The next time you feel like sharing an apple, don't worry about slicing it first — just pull the stem, get a good grip, and use your bare hands! Be warned if you're a Granny Smith fan, though. Their diminutive build can complicate things.This trick can be useful even if you're not big on sharing. If you can split an apple anytime you want, then you can always check to be sure there's nothing wormy inside before you take that first bite.
How to break an apple into four slices [Instructables]