SHH and neoplasm: To address this, we developed a scalable and reproducible tumor‐forebrain‐organoid (TBO) model for ETMR and ATRT sonic hedgehog (ATRT‐SHH) using a novel coaggregation method, which we characterized histologically and transcriptionally, and applied to drug screening, thereby identifying new candidate therapeutics for ETMR (Supplementary File of Methods).