The ability to efficiently introduce foreign molecules into cells constitutes an important tool in any laboratory and facilitates studies of gene regulation and protein function. A plethora of transfection methods have been developed for transfer of DNA into mammalian and animal cells. Those methods either utilize the physicochemical properties of the vector-carrier of the DNA or use mammalian viruses. In the first group of methods, some classic techniques are well-known, such as: calcium phosphate, DEAE-dextran, electroporation liposome-mediated delivery, direct microinjection/biolistic particle delivery, and non-liposomal multi-component reagents. Viral vector systems use both DNA (Adeno-) and RNA (Retro-, Lenti-) viruses. more