Two back‑to‑back Nature Biotechnology papers provide in vivo tools to quantify endosomal escape of nucleic acid payloads and evaluate lipid nanoparticle (LNP) chemistries for liver delivery. One study describes an in vivo endosomal escape assay; the other uses a lysosomal barcoding strategy to benchmark branched ionizable lipids and identify structural features linked to potent hepatic delivery. Both papers deliver actionable metrics for a long‑standing bottleneck in RNA therapeutics: measuring and optimizing the fraction of internalized material that escapes endosomes to reach cytosolic targets. The techniques are poised to accelerate rational LNP design, de‑risk translational candidates, and inform industrial formulation efforts for mRNA and gene‑editing modalities.