Abstract: A micronizer includes a housing having a chamber in which a vertical array of impeller discs is disposed. Impact members are disposed on the impeller discs. One, or more, of the impellers have impact members that overhang circular peripheral edges of the impeller discs. The rotational speed of the array of impeller discs may be varied by adjusting the speed of a variable drive motor. The rate of air flow through the array of impeller discs may be varied by adjusting the speed of a fan, which is independent of the speed of the array drive. A plurality of air deflector plates mechanically cause downward force vectors to deflect a combined pulverulent air-material mixture downwardly toward said rotating impact members.