The "disperse system formalism" (DSF) can be used to describe the structure of physical and chemical systems at any scale. It is particularly useful for describing the microstructure of colloidal systems that are ubiquitous in food. Adapting a computer program that was already used for the study of complex gels, the whole set of possible suspensions was determined for the first "classes", i.e., groups of systems ordered by increasing number of complexity. Here a detailed discussion of the impossible formulae is given, and it is explained how the classes were obtained. It is shown that 6 possibilities exist for the class 1.1 suspensions (one solid phase only dispersed in one monophasic liquid phase); for the class 2.1, there are 362 systems. A generalization to complex solid suspensions, and to emulsions, foams and aerosols is proposed.