Since 1994, a growing number of foods were developed using genetic modification (GMO). With these products has come controversy, primarily in Europe where some question whether GMO foods are safe. Scientists are now able to use the tools of modern biotechnology to insert a gene into the crop to give it new, advantageous characteristics. Most genetic modifications make it easier to grow the crop. About half of the American soybean crop planted in 1999 carries a gene that makes it resistant to an herbicide (Roundup) used to control weeds.