Submicro- and nanocrystals of a d-f heteronuclear coordination polymer, La[Fe(CN)(6)]center dot nH(2)O, were prepared in the water-in-oil microemulsion using AOT or NP-5 as a surface-protecting agent. When AOT was used, size and shape of the crystals were remarkably influenced by their preparation conditions, whereas little changed when NP-5 was used. These results were explained by the different protecting abilities of anionic AOT and nonionic NP-5.