Abstract: The invention relates to a method of manufacturing a product having a sub-micron primary particle such as metal oxide, metal oxidhydroxide or metal hydroxide product, said method comprising the steps of: introducing a solid reactor filling material in a reactor, introducing a metal-containing precursor in said reactor, introducing a co-solvent into the said reactor, introducing a supercritical solvent in the said reactor. By these steps a contact between the metal-containing precursor and the co-solvent is established, thus resulting in the formation of said product in the proximity of the said solid reactor filling material. The present invention offers the astonishing possibility of producing anatase phase of TiO2 at temperatures as low as between 50° C. and 100° C. and at concurrent pressures of 100-200 bar. The invention also relates to a product such as anatase TiO2 produced by the method and also relates to an apparatus utilising the method.