Scientists are growing human organs in pigs

Best put down that sausage sandwich for the following read.

Scientists at the University of California have taken the controversial step of injecting human stem cells into pig embryos. 

These human-pig embryos - known as chimeras - will develop 'naturally' in a sow for 28 days, at which point they'll be terminated to allow the research team to test the tissue development. If successful, the embryo will contain a pancreas consisting of only human cells amongst its other piggy organs. 

Research leader Pablo Ross told the BBC: "Our hope is that this pig embryo will develop normally but the pancreas will be made almost exclusively out of human cells and could be compatible with a patient for transplantation."

The experiment forms part of ongoing research aimed at countering the worldwide shortage of transplant organs - in effect, saving our bacon with bacon. 

Such is the controversy of the research that the US medical research agency the National Institutes of Health banned grant funding for such experiments in September 2015. 

While groundbreaking, the ethics of "playing god" with the innards of animals has raised major concerns from biologists and animal rights groups. One tail-curling fear surrounds the possibility that the implanted human cells could migrate to other regions of the developing pig, such as its brain, making it more human than intended. 

"We think there is very low potential for a human brain to grow, but this is something we will be investigating," said Ross. It's a notion that'll be particularly chilling for anyone who's read Margret Atwood's 2003 novel Oryx and Crake, in which human-pig chimeras plague the wild life of a dystopian future.

The idea of growing human organs in animals is far from new: clinical trials in the nineties came to an end after researchers became fearful that any human organs developed inside other animals might result in humans becoming infected with animal viruses.

Further details of the study will be unveiled in an episode of the BBC's Panorama programme, Medicine's Big Breakthrough: Editing Your Genes. Tune in to BBC One tonight at 8:30 if you want to scare yourself silly.