The key to the new 'brain in bottle' 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 surrounded a ventricle-like inner cavity and mimicked the layered structure of a human brain growing within a developing foetus.
More top news
Drink lots of water, stay out of the sun during the middle of the day, and take particular care of vulnerable people.
The 81-year-old has disappeared from his home on the Spanish island on the hottest day of the year so far.
A video shows firefighters hosing off four bulls while they rescued a cow that had become trapped between two trees.