The present invention relates to a process for the preparation of a stable dispersion of particles, particularly sub-micron particles in an aqueous medium and to a stable dispersion of particles in a liquid medium. The process provided comprises the following steps: 1) combining a) an emulsion comprising a continuous aqueous phase; an inhibitor; a stabiliser; with b) the substantially water-insoluble substance; and 2) increasing the temperature to vicinity of the melting temperature of the substantially water-insoluble substance. The sub-micron dispersion provided exhibit reduced or substantially no particle growth during storage and reduced crystallisation rate of the substantially water insoluble active compound.