Although colloidal dispersions are used in numerous areas of science and technology, very few colloidal systems are produced solely because of their colloidal nature. The scientists in industry have to understand the laws of colloidal systems in order to improve, e.g., applicability of materials, to find new fields of applications, to develop new products. Methods for stabilizing or destabilizing colloidal systems are indispensable for practical applications. For example, it may be necessary to produce a dispersion that is stable for a long period of storage but that destabilizes during application. Thus, it is important to understand the principles that determine the stability or instability of colloidal systems. Volume 4 describes the role of colloids and interface science in agrochemicals.