Researchers engineered Cas9 variants to refine prime editing precision, developing successive editors (pPE, xPE, vPE) that reduce byproduct indels while maintaining efficiency across diverse edits. The approach relaxes nick positioning to favor degraded competing ends and achieved edit:indel ratios up to 543:1 with fewer off‑target effects in human cells and mouse embryonic stem cells. Complementing that, teams reported in situ sequencing approaches to measure base and prime editing outcomes directly in tissues of mice and macaques, improving spatial and quantitative readouts of editing efficiency and off‑target events. The combined methodological advances push gene editing toward safer and more measurable therapeutic application. Technical clarity: Prime editors install precise edits without double‑strand breaks but remain prone to small insertion/deletion byproducts; mutational tuning of the Cas9 nickase addresses that limitation and enhances translational prospects.