 Over the next five minutes, I want to tell you how the convergence of stem cell biology, material science, advanced manufacturing, and medicine will make organ repair and replacement commonplace. My lab studies heart disease, the leading cause of death worldwide. During a heart attack, the heart becomes starved for blood, ultimately leading to organ failure. The challenge is that the heart cannot regenerate following injury or disease. You are born with roughly 3 billion heart muscle cells, or cardiomyocytes, and this number remains relatively constant throughout life. Cardiomyocytes cannot divide to increase cell number, so once lost, they're gone forever. Transplantation is the only cure for end-stage heart failure, and is remarkably successful, with patients living 10 or more years. However, the number of donated hearts is critically limited, with less than 5,000 transplants performed per year worldwide. So the need is tremendous. There are millions of people that need a new lung, liver, kidney, or other organ. Human-induced pluripotent stem cells, or IPS cells for short, have emerged as a powerful technology that can turn an adult skin cell into a new heart muscle cell. This has all the advantages of embryonic stem cells, but without the ethical concerns. So we can now generate new human heart muscle cells at large scales. Researchers have injected these stem cells into damaged hearts. However, they have not achieved large-scale regeneration. This strongly suggests that injecting stem cells alone is not enough, and that we need to provide these cells with an instructive environment to guide regeneration. We need a scaffold. Researchers have taken adult hearts and dissolved away the cells, leaving behind a complex 3D scaffold of collagen and other protein fibers. They've seated heart muscle cells on these scaffolds and shown the ability to reform heart muscle. But is the adult heart really the appropriate environment to guide regeneration? Instead, my lab is looking to developmental biology for answers and inspiration. Human heart muscle only forms during embryonic development. By understanding driving principles of heart formation, we can engineer biomimetic scaffolds to guide heart repair. But even the embryonic heart is incredibly complex. This is where 3D printing provides a transformative capability. 3D printers build objects layer by layer, with most depositing molten plastic through a tiny heated extruder controlled by a robotic system in all three dimensions. It is a machine that can make almost anything. Surgeons now practice complex surgeries using 3D printed plastic models from CT and MRI imaging data, increasing success rates. 3D printers can now build medical devices such as custom plastic skull plates, custom matched to the patient's unique anatomy. But how do we extend this to 3D printing living tissue? Imagine you had in front of you a pocket watch disassembled. Most of us could start to reassemble the gears. But what if those gears were soft and flexible? How would you hold everything in position during that assembly process? This is the challenge of 3D printing soft materials and building them into complex structures such as blood vessels. In my lab, we have developed a new technology to 3D print soft tissues inside a temporary support gel. When the needle of the 3D printer moves through the support gel, it generates enough force to move easily, but anything extruded stays exactly in place. When finished, we simply melt away the support bath at body temperature. We call this fresh printing. By combining fresh printing with developmental biology, we can now engineer biomimetic scaffolds for heart repair. First by imaging the embryonic heart in 3D, second by building a 3D computer model from that data, and third by 3D printing a biomimetic scaffold that matches the composition and mechanics of native heart. In the lab, we can now build beating human heart tissue. To do this, we combine stem cell-derived heart muscle cells, support cells, and blood vessel cells together with a protein-based bioink that supports tissue formation. We are working to rapidly increase complexity towards building a 3D organ. Translating a 3D printed organ into the clinic is going to take decades, but it will happen. And while I have described the process for the heart, it's one we believe can be expanded to lung, liver, and other areas of critical need. This is why we are making our hardware and software freely available to accelerate innovation by our lab and others. Now, there are challenges to achieving this vision. High-risk, high-reward research requires large-scale funding and support, and both public and private investment that translate these technologies into new industries. But together, we have the opportunity to move 3D bioprinted organs from the realm of science fiction and into clinical reality. Thank you.