A simple method for the preparation of charge-stabilized Prussian Blue nanocrystals (PBNs) of readily adjustable size is reported. PBNs have been purified by addition of non-solvents and redispersed in water without aggregation. PBNs may be electrostatically arranged along isolated polycation (PC) chains adsorbed onto flat surfaces. PC-PBNs nanohybrids constitute useful materials for the manufacture of electrooptical devices. PBNs can be also used as contrasting reagent to improve AFM visualization of positively charged polymer chains deposited on substrates of relatively high roughness.