This is a huge discovery that brings on possibilities for studying the early development of brain disorders.

It also has left some scientists feeling hesitant.

These lab-grown brains are known as organoids - three-dimensional, miniature, simplified versions of organs grown in a lab for research purposes, such as testing drug responses, or cell development under certain adverse conditions.

The research was first presented at a conference back in November 2018, and has now been peer-reviewed and published in Cell Stem Cell.

"The level of neural activity we are seeing is unprecedented in vitro," says neuroscientist Alysson Muotri from the University of California, San Diego.

"We are one step closer to have a model that can actually generate these early stages of a sophisticated neural network."