Transfection: Transfection is the transfer of foreign DNA into cultured host cells mediated through chemicals. The charged chemical substances such as cationic liposomes, calcium phosphate of DEAE dextran are taken and mixed with DNA molecules. The recipient host cells are overtaxed by this mixture. Consequently the foreign DNA is taken up by the host cells. 

Electroporation (Electric Field-mediated Membrane Permeation): In electroporation an electric current at high voltage (about 350 V) is applied in a solution containing foreign DNA and fragile host cells. This creates transient microscopic pores in cell membrane of naked protoplasts. Consequently foreign DNA enters into the protoplast through these pores. The transformed protoplasts are cultured in vitro which regenerate respective cell walls.

Microinjection : In this technique foreign DNA is directly and forcibly injected into the nucleus of animal and plant cells through a glass micropipette containing very fine tip of about 0.5 mm diameter. It resembles with injection needle. In 1982, for the first time Rubin and Spradling introduced Drosophila gene into P-element and microinjected into embryo. 

Particle Bombardment Gun (Biolistics): This technique was developed by Stanford in 1987. In this method macroscopic gold or tungsten particles are coated with desired DNA. A plastic micro-carrier containing DNA coated gold/tungsten particles is placed near rupture disc. The particles are bombarded onto target cells by the bombardment apparatus. Consequently foreign DNA is forcibly delivered into the host cells.