Two independent Nature Biotechnology reports introduced quantitative, in vivo assays that measure endosomal escape of lipid nanoparticles (LNPs) in the liver and used those readouts to optimize delivery chemistry. One paper described a lysosomal barcoding approach to track nucleic acid escape; the other deployed in vivo functional assays to map how branched ionizable lipids perform inside hepatocytes. Both studies translate a long‑standing bottleneck—poorly characterized endosomal escape—into a measurable design parameter. Authors showed how lipid structure correlates with cytosolic release and potency, offering design principles that could improve RNA therapeutic potency and reduce required doses for hepatic targets.