The nanoscale parameters of metal clusters and lattices have a crucial influence on the macroscopic properties of materials. Herein, we provide a detailed study on the size and shape of isolated yttrium carbide clusters in different fullerene cages. A family of diyttrium endohedral metallofullerenes with the general formula of Y2C2n (n = 40-59) are reported. The high field C-13 nuclear magnetic resonance (NMR) and density functional theory (DFT) methods are employed to examine this yttrium carbide cluster in certain family members, Y2C2@D-5(450)-C-100, Y2C2@D-3(85)-C-92, Y2C2@C-84, Y2C2@C-3v(8)-C-82, and Y2C2@C-5(6)-C-82. The results of this study suggest that decreasing the size of a fullerene cage with the same (Y2C2)(4+) cluster results in nanoscale fullerene compression (NFC) from a nearly linear stretched geometry to a constrained "butterfly" structure. The C-13 NMR chemical shift and scalar (1)J(YC) coupling parameters provide a very sensitive measure of this NFC effect for the (Y2C2)(4+) cluster. The crystal structural parameters of a previously reported metal carbide, Y2C3 are directly compared to the (Y2C2)(4+) cluster in the current metallofullerene study.