Cationic lipid transfection reagents are synthetic molecules that possess a positively charged polar head and one or two hydrophobic chains. These molecules can form liposomes, spherical vesicles, which contain the nucleic acids to be delivered into cells. The liposomes merge with the cell membrane and release the nucleic acids into the cytoplasm or the nucleus. Cationic lipid transfection reagents can be used to introduce different types of nucleic acids, such as DNA, RNA, or proteins, into various types of cells, including animal, plant, or bacterial cells. The objective of cationic lipid transfection is to modulate gene and protein expression within the cellular context. Cationic lipid transfection can serve as an analytical tool to study and regulate genetic functions and interactions, molecular mechanisms of diseases, and the effects of gene therapy. Cationic lipid transfection can also contribute to the development of nucleic acid-based drug discovery and vaccine strategies, offering promising perspectives for the treatment of numerous diseases.