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Diffusion kinetics can regulate organoid size and health: upon reaching a certain size, organoids have arrested growth and develop a necrotic core. This process is possibly linked to a switch from a proliferative, stem-like state to a non-proliferative, diﬀerentiated state, as well as necrosis of the organoid core. Terminal diﬀerentiation can be a strategy to limit organoid size but preventing a necrotic core is crucial for organoid health as it could lead to premature differentiation. Perfusion/flow of nutrients around the organoids is a technology that has been discussed in scientific literature to assist with prevention of necrotic core. Organoid vascularization is an important criterion for long term culture; seeding endothelial cells within the system to allow for formation of blood vessels (neo-angiogenesis) as well as using bioprinting to engineer the architecture and placement of cells are important platforms that are being explored towards this objective. Included below are two links to helpful articles on the topic.