The tiny hollow “organoids”, measuring three to four millimetres across, have a structure similar to that of an immature human brain including defined regions.
But the scientists insist they are still a long way from building a working artificial brain – or even replacement parts for damaged brains.
The goal was to produce a biological tool that can be used to investigate the workings of the brain, better understand brain diseases and test out new drugs.
One expert said the “audacious” discovery could lead to the future creation of a simple animal-like brain that could be linked to sense organs and had the ability to learn.
Other laboratory “models” of human organs have previously been grown from stem cells, including those replicating the liver, intestine, pituitary gland and eye.
The key to the new research involved nourishing immature cells in a gel-like “matrix” that allowed the complex organoid structures to develop.
These were then transferred to a spinning bioreactor which provided extra nutrients and oxygen, enabling them to grow much larger in size.
After two months of development the “mini-brains” had become globular spheres up to four millimetres in diameter. Each one mimicked the layered structure of a human brain growing within a developing foetus.