Self-assembled monolayers of carboxylic acids on a silver surface underwent a reversible reorganization process to form discrete clusters of hydrogen-bonded free acids upon exposing the monolayer assembly to H2S vapor. The clusters had a wide range of sizes, from nearly one micrometer to tens of nanometers or smaller. Restoration of the monolayer film from the clusters, driven by the reaction between the carboxylic acid molecules and the basic surface sites, proceeded on the surface through surface migration of molecules in the clusters. The process was real-time imaged by tapping mode atomic force microscopy.