Microbial links are obligate in any food chain in soil, because detritivorous animals derive essential amino acids and other resources from microorganisms. To degrade recalcitrant substrates such as cellulose, soil animals do not produce their own cellulase, but they use cellulases derived from gut microorganisms. We argue that in detrital food-webs, carbon (energy) is usually not a limiting factor. Other elements, for example nitrogen and phosphorus, are present in ratios (relative to carbon) which are lower in the food than in the animal itself, and are more likely to be limiting. This implies that we need to consider the dynamic stoichiometry of N, P and C in the food-web and we cannot assume a fixed ratio between the three elements. In addition, detrital food-webs consist of communities at three different scales. The bacteria-algae-Protozoa compartment is nested inside the fungi-microarthropod compartment and this is in turn is contained within the earthworm-rhizosphere compartment. Animals of the higher levels consume communities of the lower levels as a whole. Present approaches for the structure of detrital food-webs do not take this nested structure into account. Our hierarchical concept of food-web structure may explain why soil pollutants that are not directly toxic to animals, may still affect the functioning of soil animals, either through deterioration of their food resources or through effects on internal food-chains.