People requiring organ transplants face a number of hurdles to overcome including waiting for a transplant to become available, their body potentially rejecting the new organ, and the limited life span of that organ. It would be much better if we could grow new organs on demand using our own cells, and Japan might be the first country to do it.New guidelines have been put forward to the Japanese government to advance embryonic research beyond today’s imposed limits. At the moment, scientists are allowed to develop chimeric embryos (human stem cells added to an animal embryo) for no more than 14 days in a lab setting. The new guidelines would allow that chimeric embryo to be implanted into the womb of an animal and grown into a working human organ.Those guidelines, if accepted, would replace the existing restrictions within 12 months. After that, human organs can start to be grown and the process perfected for an actual transplant to occur.The animal most likely to be used for organ growth is a pig, and the first human organ to be grown would be a pancreas. If successful, it means people with diabetes will benefit first. Then scientists can start growing and perfecting more complex organs, such as the human heart and kidneys.If all goes to plan, animal-to-human organ transplants could be viable within 5 years. Unfortunately, harvesting the organ does mean killing the animal, however, the scientists are confident that eventually we’ll be able to grow multiple organs at once within the same womb.