If the end goal is to be able to grow replacement tissue for all parts of the body, sooner or later you will arrive at the engineering of male genitals. In fact sooner, it seems, which isn't much of a surprise given human nature. Via EurekAlert!: "In an advance that could one day enable surgeons to reconstruct and restore function to damaged or diseased penile tissue in humans, researchers have used tissue engineering techniques to completely replace penile erectile tissue in animals. ... After implantation with the replacement tissue, the rabbits had normal sexual function and produced offspring. ... Further studies are required, of course, but our results are encouraging ... Reconstructing damaged or diseased penile erectile tissue has traditionally been a challenge because of the tissue's unique structure and complex function. There is no replacement for this tissue that allows for normal sexual function. ... The scientists first harvested smooth muscle cells and endothelial cells, the same type of cells that line blood vessels, from the animals' erectile tissue. These cells were multiplied in the laboratory. Using a two-step process, the cells were injected into a three-dimensional scaffold that provided support while the cells developed. As early as one month after implanting the scaffold in the animal's penis, organized tissue with vessel structures began to form."