Mesoscopic self-organization in evaporated polymer solutions was investigated. The structure of dried films was studied with optical and SEM microscopy. Formation of mesoscopic cells was studied in situ with a shadowgraph technique. Intensive migration of the vapor bubbles is an important factor in the formation of mesoscopic cells. A mechanism of mesoscopic network formation, based on the mass transport instability in evaporated film, was proposed. The impact of the solvent is discussed. (c) 2006 Springer Science + Business Media, Inc.