In precipitation processes a chemical reaction produces a sparingly soluble product which starts to precipitate as a solid via nucleation and growth. As a rule, the newly precipitated primary particles are in the nanometer size range. The behaviour of colloidal particles in this size range is governed by interfacial forces. Therefore, in most case the final product particles are secondary particles, which are built by aggregation from the fine primary ones. The final product morphology results from the action of aggregation, rheological behaviour of the suspensions and the shear rates present in the precipitator. Precipitation technology is concerned with the design and operation of such precipitators. In this paper the relevance of fundamental kinetic, collidal and rheological phenomena on precipitation technology are reviewed and discussed.