A detailed understanding of the atomic-level structure and reconstruction of the (100) facet of ceria is crucial for optimizing its performance in various thermo-, photo-, and electrocatalytic processes. Herein, the geometric and molecular orbital structures of the stoichiometric (half terminated with O), (half terminated with Ce), and (terminated with pyramids) terminations of the (100) ceria surface were thoroughly investigated using periodic (HSE06 and PW91+U DFT) calculations and first-principles thermodynamic modeling, complemented by an extended COHP analysis. The structure and the stability of these terminations were analyzed, for the first time, in terms of three generic building blocks, including bridging , square pyramidal , and tandem units and characterized with molecular orbital resolution. The atomic-wise COHP profiles were decomposed into the orbital-wise interactions within the building units, and the associated overlaps between the 4f;5s,p,d;6s-Ce and 2s,p-O orbitals were presented in the form of 2D maps with the IpCOHP values gauging their strengths. The key bonds and orbital interactions responsible for the stability of the particular building block were identified, providing a detailed molecular rationale for the thermodynamic stability order of the terminations. The predicted coexistence of the and terminations was finally confirmed by HR-TEM imaging of euhedral nanocubes supported by image simulations. Ceria nanocubes were synthesized by the hydrothermal method without surfactants.