This review describes recent advances in the supercritical (SC) CO2-continuous microemulsions, compressed CO2-expanded water-in-oil microemulsions, and compressed CO2-induced water-in-oil microemulsions, and pays more attention to tuning the aggregation behavior of surfactants in liquid solvents using compressed CO2. The applications of these microemulsions in synthesis of nanomaterials and chemical reactions are also discussed briefly. (C) 2008 Elsevier B.V. All rights reserved.