transplantation of an organ, tissue, or cells between two different species
About the word:
The Latin xeno- comes from the Greek word xenos, meaning "stranger" or "guest."
Cross-species transplants were (unsuccessfully) attempted in the 17th century.
In the late 20th century, scientists transplanted primates' hearts, kidneys, and livers into humans with some success. Pigs have replaced primates as the prime candidates for xenotransplantation to humans, but the process remains experimental and controversial.