Every day in the United States, 17 people die waiting for an organ transplant, and every nine minutes, another person is added to the transplant waiting list, according to the Health Resources and Services Administration. One potential solution to alleviate the shortage is to develop biomaterials that can be three-dimensionally (3D) printed as complex organ shapes, capable of hosting cells and forming tissues. Attempts so far, though, have fallen short, with the so-called bulk hydrogel bioinks failing to integrate into the body properly and support cells in thick tissue constructs.