Tiny human brains capable of thinking for themselves have been grown in a dish, according to scientists.
Their creator, US toxicologist Thomas Hartung, says the brains could be used to test drugs - and he hopes to set up a production line by the end of the year.
While this may sound like something out of a horror film, a plentiful supply of identical mini-brains - which are only the size of a fly's eye - could help speed the quest to cure conditions such as Alzheimer's.
"Ninety-five per cent of drugs that look promising when tested in animal models fail once they are tested in humans at great expense of time and money," Professor Hartung told the American Association for the Advancement of Science's annual conference in Washington DC.
"While rodent models have been useful, we are not 150-pound rats. And even though we are not balls of cells either, you can often get much better information from these balls of cells than from rodents.
We believe that the future of brain research will include less reliance on animals, more reliance on human, cell-based models."
Professor Hartung, of Johns Hopkins University in Baltimore, Maryland, started with samples of human skin. He then used vitamins and chemicals to turn these into stem cells - blank cells with the ability to turn into other cell types.
Finally, he used a different chemical cocktail to turn them into brain cells.
Over the next eight weeks, these balls of cells grew into tiny brain-like structures.
They contained six types of cell found in the human brain and, tantalisingly, these "talked" to each other via electrical signals - evidence of primitive thought.
But Professor Hartung added: "These brains have no input - no eyes, no ears ... there is no possibility that they would react or build up consciousness."
- Daily Mail