We present a first-principles study to elucidate the nature of the bonding, stability, energetics, and dynamics of individual X8H8 molecules (X = C, Si, Ge). The results obtained from both "local basis" and "pseudopotential" ab initio methods are in good agreement with the experimental data that exists for cubane (C8H8). The trends among these molecules are reminiscent of those prevailing in the bulk solids of C, Si, and Ge. High-temperature dynamics and fragmentation of X8H8 were studied by the quantum molecular dynamics method which shows that at high temperatures cubane is transformed to the 8-fold ring structure of cyclooctotetraene.