We synthesized cubic nanoassemblies of octahedral CeO(2) nanocrystals by simply heating an aqueous solution of cerium nitrate (Ce(NO(3))(3)) in the presence of hexanedioic acid (HOOC(CH(2))(4)COOH) in a lab-scale plug-flow reactor. It was concluded that the octahedral shape of the primary CeO(2) nanocrystals plausibly leads to octa-coordination of the primary nanocrystals, thus enabling controlled assembly to form a cubic structure.