sentences:  In the late 1990s, this concept became a partial reality when scientists in Japan developed chicken female sperm by injecting bone marrow stem cells from a female chicken into a rooster's testicles.This technique proved to fall below expectations, however, and has not yet been successfully adapted for use on humans.Creating female sperm was first raised as a possibility in a patent filed in 1991 by injecting a woman's cells into a man's testicles, though the patent focused mostly on injecting altered male cells into a man's testes (to correct genetic diseases).