Two independent teams introduced quantitative in vivo assays that measure lipid nanoparticle (LNP) endosomal escape and used the readouts to improve hepatic delivery. Groups publishing in Nature Biotechnology deployed lysosomal barcoding and related lysosomal/escape reporters to quantify endosomal escape in mice and benchmark branched ionizable lipids and LNP chemistries. The lead result: measurable differences in escape efficiency correlate with potent liver delivery and functional payload release. By converting endosomal escape from a black box into a quantifiable in vivo metric, the studies give formulators an empirical lever to prioritize LNPs for therapeutic mRNA and gene‑editing programs. Authors show how escape kinetics map to potency in liver models and outline actionable design rules for ionizable lipid structures and lipid blends to raise cytosolic delivery rates in preclinical systems.