Tiny human almost-brains made in lab

Largely left to their own devices, human stem cells knitted themselves into tissue with a multitude of brain structures and specialized cadres of neurons in a form reminiscent of the brain of a nine-week-old fetus, scientists report August 28 in Nature.

The tissue doesn’t approach the dizzying complexity of the human brain. Yet these tiny neural balls, each no bigger than a BB pellet, represent the most complex brain structure grown in a lab to date, researchers say. The new work could provide an unprecedented window into the early stages of human brain development, a simple way to test pharmaceuticals on human brain tissue and a way to study the brain defects of individual patients, the study authors suggest.

“They’ve done something very remarkable,” says Flora Vaccarino of Yale University.

After about two months of growing in a nutrient broth,