The paper is dedicated to a major topic of Grain Boundary Engineering: evolution and stability of granular microstructures. The various mechanisms of grain microstructure stabilisation are considered. The role of grain boundaries, vacancies and especially triple junctions as dragging factors in grain growth of polycrystals is comprehensively discussed. A hierarchy of efficiency of different mechanisms for grain growth inhibitionis presented. It can be utilized as a basis for an assessment of the stability of fine grained and nanocrystalline materials. (C) 2005 Springer Science + Business Media, Inc.