The Organ Care System keeps lungs warm, breathing and nourished while outside the body. MediCommConsultants hide caption

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"Liver buds" grow in petri dishes. The rudimentary organs are about 5 mm wide, or half the height of a classic Lego block. Courtesy of Takanori Takebe/Yokohama City University Graduate School of Medicine hide caption

itoggle caption Courtesy of Takanori Takebe/Yokohama City University Graduate School of Medicine

Sarah Murnaghan, on May 30, as she and her parents marked the 100th day of her stay in Children's Hospital of Philadelphia. Murnaghan family/AP hide caption

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Surgeons transplant a kidney in 8-year-old Sarah Dickman at Children's Healthcare of Atlanta in 2008. The proposed changes in the transplant list attempt to maximize kidney life in young patients. John Bazemore/AP hide caption

itoggle caption John Bazemore/AP

A kidney donor is wheeled to an operating room for a transplant at Johns Hopkins Hospital in Baltimore in late June. Brendan Smialowski/AFP/Getty Images hide caption

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Most living kidney donors return to their daily lives in a matter of weeks, but for some, unforeseen physical and financial complications arise. iStockphoto.com hide caption

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Scarlette Wiens touches the chin of her father, face-transplant recipient Dallas Wiens. Lightchaser Photography/Brigham and Women's Hospital hide caption

itoggle caption Lightchaser Photography/Brigham and Women's Hospital

Robert O'Rourke was diagnosed with idiopathic pulmonary fibrosis in late 2006. The lung disease causes scarring in the lungs, which makes breathing difficult. Courtesy of Robert O'Rourke hide caption

itoggle caption Courtesy of Robert O'Rourke