This is the first time anybody has been able to get a working organ in a mammal to rejuvenate itself, The Economist reports. It's a step forward for this particular method organ regeneration. Of course, many labs have grown artificial organs in different ways. We've covered everything from a trachea, made from the patient's own stem cells, to 3-D printed organs. Some of these, such as the trachea, have already been used in people.