Microparticles with controlled porosity have been widely used in various applications. In this Full Paper, a new method of freezing emulsions has been developed to prepare porous microparticles with unique aligned porosity. Aligned porous poly(epsilon-caprolactone) microparticles are formed on an aligned porous polymeric composite. The aligned porous microparticles can be released simply by dissolving the supporting composite in water. The formation mechanism for the aligned porosity is discussed. The effects of freezing temperature and stirring speed are investigated. This method is also demonstrated to be generic in preparing porous microparticles with controlled porosity. As an example, polystyrene microparticles with different types of pores are produced. A preliminary study on the application of the-porous microparticles in supporting stem cell growth is performed. It is found that poly (c-caprolactone) microparticles can support the growth of mouse embryo stem cells.