We developed the simple contrasting procedure to improve AFM visualization of single positively charged polymer chains via counterion exchange between Cl- anions and bulky hexacyanoferrate anions or negatively charged nanoclusters of Prussian Blue. This method allowed us to increase thickness of the resulting structures up to 10 nm and, consequently, to provide visualization of isolated polymer chains deposited on a glass surface (root-mean-square roughness about 1 nm). In contrast, the contrasting with relatively large PB clusters (more than 10 nm in size) distorts conformations of the molecules and even eventually leads to a fragmentation of polymer chains.