Аннотация:Application of the magnetic ferrocolloidal liquids on samples with magnetic and nonmagnetic parts in their composition actually visualizes the structure of magnetic particles, namely: magnetite-ilmenite intergrowths, heterophase decay structures, grain distribution of zones with different magnetization, and under certain conditions it is possible to diagnose domain structure, including the determination of the domain walls dimensions. In this paper there are presented overviews of experimental works on the study of the magnetic microstructure of samples from various collections with magnetic fluids and micrographs of the studied structures with magnetic contrast usage obtained with a ferrocolloid application.