Editing is stochastic and non-saturating, which means two cells from different times or different lineages can end up with the same lineage mark at the same site. How's the editing efficiency?

This paper has a limitation on the labeling window : In vitro window 24hr + In vivo window (E2.5 to harvest time). Cre was activating throughout the developmental time. The molecular clock in PEtracer is a per-cell division clock, not a per-developmental time clock. That means PEtracer requires constant cell-division rate across all cells, stages and lineages — I don't believe it’s possible in real development.