Test tube brains may sound like something out of a dystopian science fiction or horror movie, but scientists are using them to understand Alzheimer's disease, Parkinson's disease, and traumatic brain injuries, and even detect these conditions early.Now, according to research published in the American Chemical Society’s Biomaterials Science & Engineering journal this month, these mini-brains can survive for at least nine months when grown in a mixture of protein from silk and stem cells from patients with diseases like Alzheimer's and Parkinson's. Artificial mini-brains typically have a short life span, but these long-lasting brains allow scientists to observe the progression of neurological diseases in groups of cells over time so that they can pin down the earliest signs of disease onset.To be clear: the goal of these “mini-brains” isn’t to replace a human brain. Rather, the purpose of these mini-brains is to understand how the human brain works and figure out how to treat neurological diseases. Ethical quandaries always arise when testing medication on humans and animals. Meanwhile, mini-brains have the advantage of being alive and able to exhibit “spontaneous electrical activity,” but they’re not conscious in the way that a living brain is .David L. Kaplan, a biomedical engineering professor at Tufts University, said in a press release that the fine-tuned test tube environments of these mini brains doesn’t just help the brain live longer; it also helps them support various types of brain cells. "The silk-collagen scaffolds provide the right environment to produce cells with the genetic signatures and electrical signaling found in native neuronal tissues,” Kaplan said. Basically, they're not just bundles of nerve cells, but different types of specialized cells that would be found in a real human brain.Tufts has been working for more than five years to develop mini-brains optimized for neurological research. Back in 2013, this research team was able to mimic the brain of a nine-week-old fetus out of stem cells taken from human skin. Then, in 2014, they tried shocking and banging these mini-brains in order to study concussions and traumatic brain injuries.Brains are not the only organ that scientists have grown from just a handful of stem cells. In fact, scientists have created a human retina in a dish, lab-grown testicles and vaginas, blood vessels, and a living layer of human skin. But the purpose of these lab-grown organs would be to transplant them into a living body in order to treat or repair certain conditions or injuries. For instance, artificial testicles could be used to help people with genital injuries conceive biological children.