An apparatus and a method for forming stabilized atomized microemulsions from different liquids which are normally immiscible; the apparatus according to the invention comprises a primary chamber (C1) and a sequence of at least two cavitation chambers (C2-C5) arranged in succession, means for feeding primary and secondary fluids into the primary chamber (C1), and means for the exit of the formed microemulsion from the last cavitation chamber (C5), the primary chamber (C1) and the cavitation chambers (C2-C5) being fluid-connected to each other by way of fluid passage means which are adapted to produce a velocity of the fluids, during passage through the passage means, which gradually increases from the primary chamber (C1) toward the last cavitation chamber (C5). The method according to the invention comprises the stage of premixing the primary fluid with the secondary fluid, followed by the passage of the premix of fluids through a succession of steps of flow at a higher velocity alternated with steps of flow at a lower velocity, the higher flow velocities gradually increasing from the first higher-velocity step to the last higher-velocity step.