Five representative C60@Cn dimers are presented in Fig. . It can be seen that as the size of the cyclocarbon increases, C60 fullerene gradually submerges into the carbon ring. When the cyclocarbon reaches C34, since the interior region of the ring is large enough to completely accommodate the C60 fullerene, the centers of the two moieties coincide exactly, forming a C34@C60 structure that is a new example of nano-Saturn. As the cyclocarbon expands further to C36, the center of the C60 fullerene spontaneously deviates from the center of the carbon ring to maximize their intermolecular attraction. IGMH is a popular method for visualizing interactions in chemical systems. The g inter function defined in the framework of IGMH is able to clearly reveal the interaction between specific fragments in terms of isosurfaces. If the isosurfaces are colored by sign(2), the interaction type can also be easily distinguished. The sign(2) colored g inter isosurfaces for C60@Cn are also shown in Fig. , where cyclocarbon and C60 fullerene are defined as the two fragments used for analysis. The g inter isosurfaces intuitively display the regions where significant intermolecular interactions occur, and the completely green color indicates that the electron density in the regions is very low, which corresponds to the typical feature of dispersion-dominated interactions. Considering that both cyclocarbons and C60 fullerene have rich π electrons and the nature of π-π stacking arises precisely from the dispersion effect between parallel distributed π electrons, and moreover, that the very flat shape of g inter isosurfaces between π-conjugated fragments in Fig. is a typical signal of π-π stacking, the complexation between cyclocarbons and C60 fullerene can be unambiguously regarded as driving by the π-π stacking effect.