In our review we consider the publications devoted to studies of influence of some characteristics of blood cells, the state of plasma, and the state of circulatory system’s vessels on the aggregation and disaggregation of erythrocytes. The aggregates are considered to be the structural elements at one of the hierarchical levels of the spatial organization of blood as a structured medium. We discuss the contradictions in the data about the role of interphase boundaries of cells, thickness of wall layer, and bio-mechanical characteristics of blood in generation of blood’s aggregates.