The gene gun, developed by Cornell University plant scientists in the early 1980s, is a method of direct gene transfer used in plant biotechnology. In order to transfer genes into plants, gold or tungsten microspheres (1 micrometer in diameter) are coated with DNA from a specific gene. The microspheres are then accelerated toward target cells (contained in a petri dish) at high speed. Once inside the target cells, the DNA on the outside of the microsphere is released and can be incorporated into the plant’s genome. This method is also known as “microprojectile bombardment” or biolistics. The survival rate of the bombarded cells varies with the rate of penetration. For example, if the particle penetration rate reaches twenty-one per cell, approximately 80 percent of bombarded cells may die.