While we can't see a four-dimensional object in our three-dimensional world, you can catch a glimpse of the fourth dimension with this hypercube pendant.
A point is a 0-dimensional object.
We can join two points to form a 1-dimensional line segment.
We can join two line segments to form a 2-dimensional square.
We can join two squares to form a 3-dimensional cube.
When we join two cubes, we form the 4-dimensional hypercube that you see in this pendant.