The article deals with the publications of recent years on the formation of galls on the leaves of flowering plants infected with four-legged mites (Acariformes, Eriophyoidea). The literature data on several parasite–host pairs were used, since there is no universal model system for the experimental analysis of this problem. The gallogenesis is a complex growth reaction that occurs in the leaf tissues under the influence of mite saliva. Data on the possibility of transmission of phytohormones and symbiotic microorganisms from parasites to gall-forming plants are considered, but an important question about the nature of agents inducing mite galls remains open. In recent years, progress has been made in the study of gene expression during the development of galls on strawberry leaves. The mite galls are characterized by the presence of nutritive tissue, and comparative cytological and molecular genetic studies of its development and differentiation are of interest. It is also necessary to analyze the role and dynamics of changes in cell proliferation during gallogenesis, since the widespread ideas about the activation of cell divisions in the early stages of gall formation are based only on a qualitative evaluation, without quantitatively taking into account dividing cells.