Since their inception in the 1950s, organ and tissue transplants have become routine surgical procedures. Medical advances have now made it possible to transplant 25 different organs and tissues, from kidneys and intestines to bones and even ligaments. The kidney is the organ most often transplanted from a living donor, and the success rate is higher for kidney transplants from living donors―about 10 percent higher than from cadavers. Transplants from living donors are especially beneficial since there are not enough cadaver donors for all those waiting, and every living donation made frees up a cadaver organ for another patient in need.    In certain situations, it is most advantageous to replace two organs when only one is in need of replacement. The original recipient’s healthy organ is then available to be transplanted into another patient. This “domino” transplantation is usually performed when the surgery for the combined transplant, such as heart and lungs, is easier to perform than the surgery on only one organ. An example is a patient in need of a double lung transplant. 　Even though the patient's original heart is functioning properly, it is removed and later transplanted into another patient rather than being discarded along with the unhealthy lungs. Regardless of the donor’s age, there is always something that can be donated, either for transplant or research. In the United States, a person under the age of 19 can become a donor with parental consent. A senior citizen's heart, which may not meet normal transplant criteria, can be transplanted temporarily in time-sensitive situations until a more suitable heart becomes available.    Regrettably, very few of the people who die each year and meet the criteria for acceptable organ donation actually become organ donors. More people need to recognize the importance of donating because they provide the gift of life to those who may otherwise be without hope.