Abstract: The invention provides a method and apparatus for forming particles of a substance, comprising (a) introducing into a particle formation chamber, the temperature and pressure in which are controlled, a first supercritical fluid (SCF) and a solution or suspension of the substance in a vehicle, (b) simultaneously introducing an impinging flow of a second supercritical fluid (SCF), at an angle to, and directed at, the direction of flow of the first supercritical fluid, so as to increase the amount of kinetic energy transferred to the solution or suspension; and (c) using either or both of the first and the second supercritical fluids to disperse the solution or suspension, and to extract the vehicle from it, substantially simultaneously and substantially immediately on introduction of the fluids into the particle chamber.