Crystallization is one of the oldest separation processes used in the chemical industry and is still one of the most important. It is also going through an exciting renaissance with the result that it is becoming yet more central to the needs of the modern chemical industry. As well as itslong-standing use in the commodity chemicals business, it is central to the fine and speciality areas. The emphasis in crystallization has thus been changing from the simple production of bulk solid particles to one in which ever higher standards and reproducibility of particle size, sizedistribution, crystal form and particle morphology are demanded in both product and process development.