The heart of a genetically modified pig has been successfully transplanted into monkey, say scientists in South Korea.
It is the first time the country has claimed to have accomplished such an inter-species operation, Daily Mail reported.
Known as xenotransplantation, it is seen by some as a way to end the chronic shortage of human organs available for transplants.
Before the controversial procedure, conducted in Seoul, the cloned pig had its genes responsible for immune rejection removed.
The ultimate aim of such experimentation would be to put pig hearts and other swine organs into humans.
And the South Koreans believe this could become a commercially viable reality within five years, the newspaper added.
The first known transplant of a genetically engineered pig heart in a primate was performed in 1994.
But the possibility of animal-to-human operations has divided the medical ethics community.