A 3D projection of a tesseract performing a simple rotation about a plane which bisects the figure from front-left to back-right and top to bottom. Also called 8-cell or octachoron, a tesseract is the four-dimensional analog of the cube, where motion along the fourth dimension is often a representation for bounded transformations of the cube through time. The tesseract is to the cube as the cube is to the square. The tesseract is the four-dimensional hypercube, or 4-cube.
Image credit: Jason Hise