Researchers have indicated that they have taken the first step towards growing human organs inside pigs. Scientists grew human cells inside pig embryos with the eventual goal of culturing human organs to transplant into people (video above).

If it works, the shortage of organs for transplant in humans could be reduced drastically.

Since our immune systems are designed to get rid of foreign elements in our bodies, transplants aren’t always successful.

The idea is to genetically modify the embryo of a pig so that it doesn’t grow its own kidneys. It is then injected with stem cells from the person who requires a transplant. As the embryo starts developing, the humans cells grow into kidneys made from the patient’s cells, which can later be harvested for transplanting.

The pig-human embryo experiments have only been carried out for a few weeks, however, and it is far too premature to assume it will work. Moreover, the question marks are not just over the biological feasibility but also the ethics.

But if it proves successful, the method can be used to grow other human body parts too, including, maybe, the brain. The video asks, “And when we do, how will we know if that pig is still a pig?”