A rotor/stator type mixer for breaking up particles is disclosed. The mixer comprises a mixer unit (14) which includes a stator (22) having a plurality of openings (11b) formed therein and a rotor (13) disposed inwardly radially of the stator and spaced away from the stator with a specific gap. The rotor includes a rotor peripheral wall (40) that faces opposite the inside of the peripheral wall of the stator. A plurality of rotor openings (41) are formed in the rotor peripheral wall. The dimensions of the features are constrained by an equation dependent on the size, number of apertures, flow rate or particles etc.
