If you're mystified by how the Nintendo 3DS
could display two images, one for each eyeball, simultaneously, without relying on glasses to divide them up, you're not alone. But you will be alone after everyone else has watched this video by Kombo's
Jeff Grubb, which explains not only the 3DS's parallax barrier system, and its effective range, but other stereoscopic 3D displays as well.
You'll also get to see a bit of off-screen 3DS footage, though looking at the 3D effect through a regular camera's view of the system just results in a kind of blurry image. And as a bonus, try to spot our own Ludwig Kietzmann! Surely you recognize the back of his head?