Mesoporous silica nanoparticles are an important class of materials with a wide range of applications. This paper presents a simple protocol for synthesis of particles as small as 40. nm and with a pore size that can be as large as 9. nm. Reaction conditions including type of surfactant, type of catalyst and presence of organic polymer were investigated in order to optimize the synthesis. An important aim of the work was to understand the mechanism behind the formation of these unusual structures and an explanation based on silica condensation in the small aqueous microemulsion droplets that are present inside the drops of an oil-in-water emulsion is put forward.