I talked w/Dr. Atala at TED. He has printed real kidney fragments, implanted them in cows, and they've produced urine. The current limiting factor is nourishment for the kidney cells during the printing process. Thus, the 'total print time' is limited, which means he can make only small kidneys at the moment. He says the likely first application will be 'augmentation' kidneys for sufferers of kidney disease, not full replacements. And this is still years away. The device on stage at TED was his actual kidney printer, but I have no idea what it was loaded with during his talk. Perhaps some low-cost filler material rather than carefully (and expensively) prepared kidney cells or stem cells or whatever it is he prints up in the lab.