English: "3D microfluidic devices to support scalability and long-term homeostasis of brain organoids. (A) Cells within brain organoids require perfusion with oxygen, nutrients, and growth factors, as well as the removal of waste products, to provide conditions approximating physiologic homeostasis. Passive diffusion penetrates to a depth of only around 300 μm, and so necrosis occurs at the core of larger organoids owing to starvation. This prevents brain organoids from being scaled up to the size and complexity required for OI research and limits their durability. (B) 3D microfluidic systems enable greater scalability and durability by providing controlled perfusion throughout larger organoids. They also enable 3D spatiotemporal dosing of chemicals for signaling purposes."