Characteristic sizes (D) were determined by magnetic measurements for two quite different types of granular system: (1) two Fe-Ag discontinuous multilayers with the overall composition of Fe5Ag95 and Fe10Ag90 (D similar to1.8 nm); (2) 10% nanocrystalline (nc) and fully nc-Fe(80)Zr(7)B(12)Cu(1)ribbons (D similar to 7 and 12 nm). X-ray diffraction could not reveal any inhomogeneity of D similar to 1.8 nm for the Fe-Ag samples. In contrast, good agreement was obtained between the cluster size determined by X-ray and magnetic methods for both nc-Fe80Zr7B12Cu1 samples. The experimental results for the Fe-Ag alloys can be reasonably explained assuming that the magnetic clusters consist of an Fe-Ag alloy phase with above 50% Ag content embedded in a matrix of an Fe-Ag alloy phase containing Ag over 95 at %. The granules in the 10% nc-Fe80Zr7B12Cu1 sample show superparamagnetic behaviour even below the Curie temperature of the amorphous residual matrix, indicating a weak coupling between the bce granules and the amorphous residual matrix.