Pulverization takes place in the central chamber of the jet mill as the process material is driven at near sonic velocity around the perimeter of the toroidal chamber by multiple jets of air. No grinding media is involved. Size reduction is the result of the high-velocity collisions between particles of the process material itself. The interior of the chamber is designed to allow recirculation of over-sized particles, enhancing the incidence and the effect of these collisions. As particles are reduced in size and progressively lose mass, they naturally migrate toward the central discharge port.