A process is disclosed for producing highly uniform silica microspheres with an average diameter of 0.1–10 µm. The process involves the hydrolysis of a silica precursor, such as tetraalkoxysilanes, in a two-phase reaction mixture. The precursor solutions are fed into a vessel at predetermined rates and compositions to form a two-phase mixture. The reaction proceeds with the formation of silica spheres, and once the two-phase mixture becomes single-phase, the spheres can be grown to the desired size by continuing the addition of precursor solutions. The process allows for the production of highly uniform spheres with controlled size and porosity. The method is characterized by the use of a two-phase liquid mixture of precursor solutions, which initially yield a two-phase reaction mixture. The process can be adapted to produce either high porosity or low porosity spheres, depending on the conditions. The invention provides a method for producing microspheres with uniform size and controlled physical properties, which can be used in various applications such as catalyst supports and high-pressure liquid chromatography. The process is carried out at temperatures between 10°C and 50°C, and the precursor solutions are combined in specific proportions to ensure the formation of two liquid phases. The method is effective in producing microspheres with a wide range of sizes and surface areas, and the results are demonstrated through various examples. The process is also applicable to growing preformed particles to larger sizes using the two-phase precursor solutions. The invention offers a significant improvement over prior art methods by providing better control over the size and porosity of the produced microspheres.A process is disclosed for producing highly uniform silica microspheres with an average diameter of 0.1–10 µm. The process involves the hydrolysis of a silica precursor, such as tetraalkoxysilanes, in a two-phase reaction mixture. The precursor solutions are fed into a vessel at predetermined rates and compositions to form a two-phase mixture. The reaction proceeds with the formation of silica spheres, and once the two-phase mixture becomes single-phase, the spheres can be grown to the desired size by continuing the addition of precursor solutions. The process allows for the production of highly uniform spheres with controlled size and porosity. The method is characterized by the use of a two-phase liquid mixture of precursor solutions, which initially yield a two-phase reaction mixture. The process can be adapted to produce either high porosity or low porosity spheres, depending on the conditions. The invention provides a method for producing microspheres with uniform size and controlled physical properties, which can be used in various applications such as catalyst supports and high-pressure liquid chromatography. The process is carried out at temperatures between 10°C and 50°C, and the precursor solutions are combined in specific proportions to ensure the formation of two liquid phases. The method is effective in producing microspheres with a wide range of sizes and surface areas, and the results are demonstrated through various examples. The process is also applicable to growing preformed particles to larger sizes using the two-phase precursor solutions. The invention offers a significant improvement over prior art methods by providing better control over the size and porosity of the produced microspheres.