A device and process for crystallizing a compound using hydrodynamic cavitation comprising the steps of mixing at least one stream of a feed solution of such compound to be crystallized with at least one stream of an anti-solvent in a nucleating section via collision of the feed solution and the anti-solvent, passing the mixed streams at an elevated pressure through at least one local constriction of flow to create hydrodynamic cavitation thereby causing nucleation and the production of seed crystals, passing the fluid stream containing the seed crystals through an intermediate section to a crystal growth section, passing the fluid stream containing the seed crystals through the crystal growth section at an elevated pressure through at least one local constriction of flow to create hydrodynamic cavitation thereby causing further crystallization of the compound contained in the solution.