Culture patterned brain organoids for extended periods (> 50 days) without the use of embedding matrices. With the essential components to prevent organoid fusion and retain a high yield of reproducible organoids, STEMdiff™ Neural Organoid Maintenance Kit is a serum-free cell culture medium designed for the maintenance and maturation of neural organoids adapted from protocols by Sergiu Pa ca (F Birey et al. Nature, 2017). When used following STEMdiff™ Dorsal or Ventral Forebrain Organoid Differentiation Kits (Catalog #08620 and #08630), STEMdiff™ Neural Organoid Maintenance Kit allows for long-term organoid experiments for neurodegeneration research, biomarker discovery, and toxicity assays. The resulting brain-region-specific organoids have a cellular composition and structural organization that is representative of the developing human forebrain. Organoids generated with these kits can also be co-cultured as assembloids to study brain region interactions (F Birey et al. Nature, 2017).