Scientists have successfully created the world's first human-monkey embryo, paving the way towards using animals for human organ transplants. The experiment was conducted in China to avoid legal issues. Researchers from the Salk Institute in the US and the Murcia Catholic University (UCAM) in Spain genetically modified monkey embryos to deactivate specific genes used in the formation of organs. The group then injected human stem cells into the embryo. If left to its own devices, the embryo would have grown into a monkey with human cells. However, in keeping with ethical standards, the scientists stopped the process long before the embryo was able to develop a central nervous system. Still, the team had to travel to China to conduct the procedure, as it was in violation of Spanish law. Estrella Núñez, who collaborated on the project, told El Pais that "the results are very promising," stating that the experiment was a necessary first step towards developing human organs in animals that