Stem cell researchers at the University of Edinburgh and the Institute of Molecular Biotechnology in Vienna grew the tiny "brain" that measures just 0.15 inches across, The Guardian reported Wednesday.
Built up of layers of brain cells with defined regions that resemble those seen in immature embryonic brains, such "organoids" could help biologists study how conditions such as schizophrenia or autism occur in the brain, the researchers said.
Though such conditions are usually diagnosed later in one's lifetime, some underlying defects occur during the brain's early development, they said.
The organoids may help in the development and testing of drugs, they said, allowing pharmacologists to test drugs in more human-like settings.
Tests on the brain cells in the organoids confirmed they were functional, researchers said.
"Previous models were pieces of small tissue that aggregated to a decent size but there was no success so far in generating something that would resemble the cortex in a particular stage of development," neurologist Juergen Knoblich said.
The research team hopes to grow larger organoids and model more brain diseases, he said, although he cautioned there could be no attempt to grow replacement brain parts or an entire brain in culture.
"I have to pessimistic about this," he said. "The ultimate complexity of the brain will not allow any replacement of structures.
"In the adult brain all the parts are intimately integrated with other areas of the brain. It would be very hard to repair defects with this."