Brain organoids are important tools to understand the formation of the human brain. However, up to now, these 3D self-assemble structures were similar to the developing human brain, from molecular (gene expression, epigenetic marks) and anatomical level. This publication reports the emergence of sophisticated neuronal networks using a novel brain organoid protocol. These networks mature over time and develop on oscillatory brain waves. Using machine learning, we compare these brain waves to electroencephalogram (EEGs) from preterm babies’ brains and showed that the maturation trajectory follows the same direction as the human brain. The work pave the way for better disease modeling and also reframe the ethical discussions about this methodology.