A researcher shows a 3D-printed heart with human tissue at the University of Tel Aviv in Israel, April 15, 2019. Tel Aviv University scientists said on Monday that they have printed the first 3D heart, by using patient's cells and materials. The heart, which was produced in a lab, completely matches the biological characteristics of the patient's heart. It took about three hours to print the whole heart. Making a human heart model is a major medical breakthrough. However, the printed vascularized and engineered heart is approximately 100 times smaller than a real human heart. (Xinhua/JINI/Gideon Markowicz)