Researchers in Japan say they have created functioning human brain tissue from stem cells for the first time.

They say it should be possible to use the tissue to test brain therapies and drugs.

One of the researchers Yoshiki Sasai from the Riken Research Centre of Kobe says scientists also hope to be able to replace damaged parts of human brains in the future.

"This is made from human stem cells called ES cells and we culture them in special conditions for about 50 days and then they grow into a two-millimetre small mushroom type of structure," he said.

"And that one resembles the structure of the foetal brain very much - a miniature brain."