Types of hierarchical polygonal shapes. (a-b) vertex-based hierarchical polygonal structures, (c) vertex-based hierarchical re-entrant HCs, (d) cell-wall-based hierarchical triangle honeycomb (HC), (e) cell-wall-based hierarchical using tetra-chiral and hexa-chiral HCs, (f) cell-wall-based hierarchical re-entrant HCs, (g) fractal-based hierarchical hexa-chiral HC, (h) fractal-based hierarchical circular polygon structures, and (i-j) spiderweb-based hierarchical hexa-chiral HCs [15].