The article provides detailed information on molecular marker technologies that are widely used in various fundamental and applied fields of science. Characteristics of the majority of existing types of molecular markers, their advantages and disadvantages are given. By being part of the genome, molecular markers carry a lot of information about its changes during ontogenesis and phylogenesis. This circumstance turns them into an excellent tool in studying evolution, systematics, genetic and epigenetic mechanisms of adaptation, as well as in creating more stress-resistant forms, in genetic mapping, genetic tagging, "genome editing", determining the quality of the surrounding environment, addressing issues of eco - and genotoxicology, diagnostics, forensic-medical expertise, etc. The results of numerous studies in which Hybridization or PCR-based molecular markers used for some of the above-mentioned purposes have been discussed as well.