There are plenty of reasons to try and stay healthy, but there’s one important benefit to keep in mind. The body’s organs are precious and almost irreplaceable; if anything happens to them, it might as well be lights out. Thankfully, medical science has tried to offer people some breathing room — because they’re almost within arm’s reach of growing fully-functional organs.

A team of scientists at the Jikei University School of Medicine in Tokyo have been working on the production of kidneys, and thus far their efforts have succeeded. They used stem cells for the organ itself, but managed to overcome a common problem with the procedure: blockage. While normal attempts at kidney production would lead to urine backing up, the latest model has extra plumbing so that everything would work and flow normally. As a result, rats with man-made kidneys have had no problems months after the procedure, and pigs have seen similar success despite their greater size.

The next step, naturally, is to see how to safely insert grown kidneys — and other organs, by extension — into humans. That requires some extensive testing, and even then the technology is admitted to be years away from practical use. On the plus side, learning how kidneys work in animals has given scientists some useful data. It’s not hard to imagine them building a stockpile for that knowledge, and one day making sure every needy donor gets fully-functional parts.