STAT3 and neoplasm: reported ≈40‐nm micelle‐cored SNAs via self‐assembly of a diblock copolymer of siRNA and poly(N‐isopropylacrylamide) for i.v. delivering siRNA against signal transducers and activators of transcription 3 (STAT3, a marker for cell proliferation) to the brain (Figure 6e).[168] The authors detected cellular entry of SNAs in brain slices (Figure 6f) and reduced tumor growth in vivo, but the cellular‐level distribution of SNAs in the brain parenchyma and tumor tissue was unclear, nor was the selectivity toward the tumor part of the brain.