Two complementary Nature Biotechnology papers described optimized live‑imaging approaches for cultured human preimplantation embryos and reported de novo mitotic errors in cells fated for trophoblast (placenta). The studies used improved labeling and long‑term imaging protocols to visualize chromosome segregation during blastocyst development. One paper reported chromosome missegregation events in placenta‑lineage cells and discussed implications for early developmental mosaicism; the other detailed methodological advances enabling prolonged imaging while preserving developmental competence. Both emphasized careful ethical and technical frameworks for embryo research. The findings bear on IVF practice, embryo selection, and fundamental human developmental biology by revealing previously unobserved mitotic dynamics in early lineages—data likely to influence research standards and regulatory discussions.