Regular Nested Structure is a geometric 3d object that is found on the quantum level after zooming into it. It resides on a different level of the Quantum Level than its counterpart. It comes in different sizes.
The quantum structure.
No mathematical entities in the real world are known by this name either. It is nested just as the Universe in the game is. There is an Irregular Nested Structure inside of every Irregular Nested Structure that you can zoom down to.