It's no longer a rare feat to 3D print blood vessels. Printing vessels that act like the real deal, however, has been tricky... until now. Lawrence Livermore researchers have successfully 3D printed blood vessels that deliver nutrients and self-assemble like they would in a human body. The key is to print an initial structure out of cells and other organic material, and then to augment it with bio ink and other body-friendly materials. With enough time, everything joins up and behaves naturally.
Right now, the actual structures don't bear much resemblance to what you'd find in a person -- you get a "spaghetti bowl" of vessels. Scientists hope to organize these vessels the way they exist in nature, though. If that happens, you could one day see artificial tissue samples and even transplants that are about as realistic as you can get.