 (E-H) Embryos at the end of cellularization co-expressing RhoGEF2-CRY2; CIBN::pmGFP, and Sqh::mCherry were mounted with the dorsal epithelium facing the objective and a region of interest (red dashed line) was defined to specifically illuminate the cell base using two-photon microscopy. A representative embryo (N=3) showing basal myosin-II from top view (sum-of-slice projection of 6 focal planes) at the initial stage of the experiment (E) and 6 min after activation (F). Z-projection of the same embryo showing the cross section of the activated region (AR) (G) and non-activated region (NR) (H) with the superimposed plasma membrane signal (CIBN::GFPpm in magenta) recorded immediately after the final Sqh::mCherry acquisition (displayed in white). The contrast has been adjusted to better visualize the distribution of myosin-II along the apicobasal axis in the respective area of the tissue. Scale bars, 20 µm 