Atomic-undercoordination-induced local bond contraction, bond strength gain, and the associated temperature (T)-dependent atomic-cohesive-energy and binding-energy-density are shown to originate intrinsically the exotic paradox of superplasticity, superelasticity, and superrigidity demonstrated by solid sizing from monatomic chain to mesoscopic grain. The paradox follows these relationships: where A, B, η 1, d and ΔT mk = T m (K)−T are size (K)-dependent physical parameters. T m(K) is the melting point. Mechanical work hardening during compressing and self-heating during stretching modulate the measured outcome extrinsically. Superplasticity dominates in the solid-quasimolten-liquid transition state. The competition between the accumulation and annihilation of dislocations activates the inverse Hall-Petch relationship. Therefore, it is essential for one to discriminate the intrinsic competition between the local bond energy density gain and the atomic cohesive energy loss from the extrinsic factors of pressure and temperature in dealing with atomistic mechano-thermo dynamics.