This question is similar to "Why are triangles, squares and hexagons the only polygons with which it is possible to tile a plane?" published here
But here, instead of a 2D environment, the question is toward a 3D context.
For example i think a possible answer is the cube. Ok, then what else?
I don't know for a 3D hexagon i have yet to be sure of what it is. In my eyes, it's more this than that.
Anyway, now you know what i mean, what are the 3D objects with which it is possible to fullfill a volume?
Regards