Brain organoids are three-dimensional clusters of brain-like tissue grown in the lab, allowing scientists to study how the brain develops, especially in cases of disease. These structures are created from pluripotent stem cells, which can become any type of cell in the body. They mimic some aspects of real human brain tissue, and have been used to study glioblastoma, a type of aggressive brain cancer. As these models become more sophisticated, they raise ethical questions about whether they might one day be considered "mini-brains." For many years, studying how the human brain develops in its earliest stages was difficult because of both technical and ethical barriers. Researchers often used animal models, but these can differ significantly from human biology. The development of brain organoids has changed this, offering a way to study human brain development in a lab setting. This has helped scientists understand how genetic changes can lead to neurodevelopmental disorders like autism, intellectual disabilities, and certain types of epilepsy. Despite their usefulness, brain organoids are still much simpler than the human brain. While simplification helps in controlled research, it can sometimes miss important aspects of brain function. Scientists have recognized that many neurological diseases involve multiple cell types and brain regions. To better mimic the complexity of the brain, researchers have created more advanced models called "assembloids," which combine different parts of the brain to reflect its natural organization. To increase the complexity of brain organoids, scientists use morphogens—molecules that replicate the chemical signals that guide brain development in the womb. These signals help cells organize themselves in specific ways, similar to how they would in a real brain. Other methods involve combining different parts of the nervous system, such as linking brain-like structures with the spinal cord and muscles, to create more realistic models. Additionally, brain organoids are being developed with more endothelial cells, which form blood vessels and help create the blood-brain barrier, a structure that plays a key role in many brain diseases, including glioblastoma. As brain organoids become more advanced and closely resemble real brain tissue, they bring up new ethical concerns. Are they just experimental models, or could they be considered more complex biological systems? While current models are still far from being true "mini-brains," scientists are seriously discussing what this might mean for research and ethics in the future.