C During the cleavage divisions the embryos define reproducible trajectories in the age/levels diagram. The trajectories of 4 embryos from n.c. 10 to gastrulation are shown (each embryo depicted with a different symbol and in a different panel). The time resolution of the time-course was 6 min. The data points are colored according to the division cycle. A time window of approximately 30 min where the trajectories stay (compatible with a steady-state), is marked with dotted-grey circles. All imaged embryos that managed to start gastrulation were included in the analysis. 