Electrophoretic Mobility Shift Assay (EMSA) is an experimental method used to study the interaction between proteins and nucleic acids. By combining target proteins with fluorescently labeled nucleic acids, forming complexes, and then performing electrophoresis in a gel, differences in migration due to protein-nucleic acid binding can be observed. EMSA can be used to analyze DNA-binding proteins, study protein-RNA and DNA interactions, and explore gene regulatory mechanisms. This simple and sensitive technique is widely used in molecular biology and gene regulation research.