The experimental motivation for this study are recent publications on cohesive granular materials. Our central question is, in which regime and by which mechanism the the movement of grains changes from movement of independent particles to a movement of small clusters with increasing cohesion. Cohesion introduces an additional length scale, so that the effects become size-dependent. The cohesive force acting on a volume element of size I x I x I is proportional to its surface, or ∝ I². The repulsive force generated by the mass of the volume element is ∝ I³. The strength of the cohesion and the density of the particles determine the size for which repulsion and cohesion are in equilibrium for a certain characteristic length d.