High-nuclearity metal complexes are a unique class of molecules. [1][2][3][4][5][6] Often in the nanoscopic size regime, they display fascinating structural diversity and possess properties that are potentially useful for developing novel catalysts, [1] materials for adsorption and storage, [2] molecular electronics, [3] optics, [4] and magnetism. [5,6] Particular interest in this field has been directed towards heterometallic complexes that feature both d-and f-block elements, and the distinct coordination behaviors of different metal ions have been observed in a large number of stunningly beautiful complexes. [7][8][9][10][11][12][13][14][15][16][17] The unique arrangement of the multiple metal centers within the complex framework, coupled with their inherently disparate electronic structures, often leads to attractive properties, of which novel magnetic phenomena such as single-molecule [14,15] and single-chain magnetism [16,17] are arguably the most notable. Our own efforts along this line of research have resulted in a number of giant 3d-4f clusters containing up to 50 metal ions. [18,19] These clusters display both stunningly beautiful structures and magnetic behaviors ranging from ferromagnetic to antiferromagnetic couplings. Herein we report the synthesis, structure, and magnetic studies of a giant heterometallic cluster containing 108 metal ions. [20] was obtained under hydrothermal conditions from a mixture of Ni(NO 3 ) 2 ·6 H 2 O, Gd(NO 3 ) 3 ·6 H 2 O, and iminodiacetic acid in deionized water and its composition was verified by satisfactory microanalysis.The four-shell, nesting doll-like structure of the cationic cluster is shown in Figure 1 a. Moving outward, the innermost shell (shell 1) contains six Ni II and two Gd III ions and is followed by shell 2 with 20 Gd III ions, shell 3 with 32 Gd III ions, and the outermost shell (shell 4) with 48 Ni II ions (Figure 1 b). The geometry of the shells approximates that of a cube. Inter-shell connections are provided primarily by triply bridging hydroxo groups, which afford a highly compact, brucite-like core structure. Similar structural motifs have been observed in both transition metal [21] and lanthanide clusters.[22] The appearance of the multi-shell structure is comparable to those of multi-shell Pd/Pt clusters, [23,24] nanocapsules of polyoxometalates, [25] and fullerene-like structures built from interpenetrating reciprocal polyhedra. [26,27] Six Ni II and two Gd III ions occupy the vertices of the cube in shell 1 (Figure 2 a). The Gd III ions, which are disposed diagonally, are bridged by an aqua ligand. Triply bridging OH groups, each of which bridges two neighboring metal ions (Gd or Ni) within the cube and a Gd III ion at the edge center of shell 2, form the 12 cube sides (Figure 2 b). The coordination sphere of each of the eight metal ions is completed by three additional m 3 -OH groups. All Ni II ions are therefore hexa-