Monitoring chemical reactions using tools of analytical chemistry is crucial for understanding the mechanisms of these reactions. In this study, leaf-like poly(p-phenylenediamine) (PpPD) microparticles were prepared with precisely tailored properties. The dark field microscopy protocol proved to be a powerful tool for studying the erosion of microparticles induced by Co(2+). Such a protocol can have the benefit of improving the understanding of reaction mechanisms and can help expand the applications of dark field microscopy. A possible mechanism was proposed to explain the experimental observations.