This method has been successfully used to deliver CRISPR Cas9 constructs to the developing brain of genetically modified mice, resulting in the formation of medulloblastoma [103], H3.3 K27M paediatric high‐grade gliomas [202] or Nf1, Pten and p53 mutant high‐grade gliomas [203]. The gene discussed is PTEN; the disease is glioma.