Scientists produced the brains in a lab and transferred it to the brain of a mouse
The blood flow will allow larger brains to be developed in the future 
Researchers hope the development can help heal stroke victims 

Miniature human brains with their own blood vessels have been grown in a lab for the first time. 

After implanting the mini-brain - which is only a millimetre long - into a mouse for two weeks, they found it had grown capillaries that penetrated all the way to its inner layers. 

The achievement could help researchers grow bigger brains in an effort to better study how the organ works.