A cerebral organoid, or brain organoid, describes an artificially grown, in vitro, miniature organ resembling the brain. Cerebral organoids are created by culturing pluripotent stem cells in a three-dimensional rotational bioreactor, and they develop over a course of months. The brain is an extremely complex system of heterogeneous tissues and consists of a diverse array of neurons. This complexity has made studying the brain and understanding how it works a difficult task in neuroscience, especially when it comes to neurodegenerative diseases. The purpose of creating an in vitro neurological model is to study these diseases in a more simple and variable space. This 3D model is free of many potential in vivo limitations. The varying physiology between human and other mammalian models limits the scope of study in neurological disorders. Cerebral organoids are synthesized tissues that contain several types of nerve cells and have anatomical features that recapitulate regions of the cortex observed in brains. Cerebral organoids are most similar to layers of neurons called the cortex and choroid plexus. In some cases, structures similar to the retina, meninges and hippocampus can form. Stem cells have the potential to grow into many different types of tissues, and their fate is dependent on many factors. Below is an image showing some of the chemical factors that can lead stem cells to differentiate into various neural tissues; a more in-depth table of generating specific organoid identity has been published since. Similar techniques are used on stem cells used to grow cerebral organoids.