Immunohistochemistry and histology of sectioned brain organoids further showed that 5‐ALA treatment resulted in the loss of GFP‐positive tumor tissue, but had no apparent effect on nontransformed neuronal tissue in the cerebral organoids, such as rosette‐like structures and MAP2 or SOX2 expressing neuronal and progenitor cells (Figs EV2M and EV3A–C). This evidence concerns the gene SOX2 and neoplasm.