One roadblock to 3D printing complete, functional organs lies in our inability to ensure the engineered tissue will be well nourished with an accessible blood supply. Presently we have seen attempts at recreating arteries and veins, but successfully ensuring blood flow deep into tissue to the level of the capillary beds has proven elusive. A group of bioengineers and clinicians have pioneered a technique allowing them to print a fibrin patch containing organized endothelial cells, the cellular linining of blood vessels. Not only did the printed patch enhance blood vessel formation, but the engineered vascular tissue actually integrated with the host's own vasculature, improving tissue perfusion of damaged tissues. This research provides a novel technique that may permit printing of larger blocks of tissue and even organs.