Life feeling a little two dimensional? Try hopping over to the fourth. This series of videos, although presenting explanations of the fourth dimension that will make your optical nerves snap, is also somehow calming. Produced by resarchers at The ENS Lyon, they’re presented in an almost pastoral style in terms of pace and narrative. Put aside a good 15 minutes to take them in if you decide to check them out. For some equally compelling but less smoothly produced retinal torture, check out this clip demonstrating some perception-bending, M.C. Escherian six-point perspective. And for a quick eye-twister, try to convince yourself that there’s only a single grid spinning in this image (full size version of image at left). Most people see anywhere from five to eight. That last one is legit, in spite of being brought to you by the guy that recently pulled of the iPhone hologram hoax.