For the first time ever, scientists are successfully 3D printing actual, living human kidneys. Like the human livers printed in the past, the kidney are currently miniature in size, but with about 90% of the printed cells being alive, the potential for human use looks immensely positive.

To produce mass amounts of the living cells, samples of human kidney cells are cultured in large volumes and blended with hydrogel, a water- and nutrition-rich material that makes up the 3D printed kidneys' base. Afterwards, the printed cells can survive for up to four months in a lab thanks to this gel's rich nutrient source.

Because the product contains living, growing cells, the actual process is considerably different from plastic-based 3D printing. According to Xu Mingen, the lead researcher and professor at a Huazhong University of Science and Technology in eastern Zhejiang Province:

It's different from traditional 3D printing—to print a cup, we have to fill up the object with our material. But this method doesn't work in cells because a cell contains blood vessels and has tissue space. We have to make sure to spare enough space for them to grow.

Most incredibly, though, these adorable mini kidneys are able to function in exactly the same ways as their real, human-bred counterpart—they can break down toxins, metabolize, and secrete fluid. All of this is fantastic news for the millions of patients in need of organ transplants every yea—a small fraction of which actually receive the life-giving surgery. And though it may still be a few years before we start seeing this method being used in actual hospitals, judging by the the success of the fun-sized version, we're well on our way to printing off brand new organs at moment's notice. [Digg]