Japanese scientists have created a functioning human liver from stem cells, according to a newspaper report.
The development, announced on Friday, raises hopes for the manufacture of organs for transplants.
A team of scientists transplanted induced pluripotent stem (iPS) cells into the body of a mouse. They grew into a small, but working, human liver, the Yomiuri Shimbun newspaper said.
A team led by Professor Hideki Taniguchi at Yokohama City University developed human iPS cells into "precursor cells", which they then transplanted into a mouse's head to take advantage of increased blood flow.
The cells grew into a human liver five millimetres in size that was capable of generating human proteins and breaking down drugs, the report said.
The breakthrough opens the door to the artificial creation of human organs, a key battleground for doctors who constantly face a shortage of transplant donors.
Taniguchi's research could be "an important bridge between basic research and clinical application" but faces various challenges before it can be put into medical practice, the Yomiuri said.
An abstract of Taniguchi's research was delivered to regenerative medicine researchers ahead of an academic conference next week, but Taniguchi declined to comment to AFP before the meeting.
Two separate teams, one from the US and one from Japan, discovered iPS cells in 2006.