Tesseract

A tesseract is a 4-dimensional object with eight cells; each cell is a cube. The tesseract is one of the six convex regular 4-polytopes. Unlike three-dimensional objects which rotate on both an axis and a plane (the plane being of length and width and the axis being of the leftover dimension, height), a tesseract rotates on two planes, one made up of length and width, and one made up of height and the fourth dimension. It is the simplest hypercube.
It is not possible to make a tesseract out of real materials. A tesseract is in four dimensions, but we can only move in three dimensions.
Example:
Line is to the 1st dimension,
Square is to the 2nd dimension,
Cube is to the 3rd dimension,
Tesseract is to the 4th dimension.