Embryos expressing RhoGEF2-CRY2/CIBN::GFPpm and the membrane marker GAP43::mCherry were mounted with the ventral epithelium facing the objective. To analyze apical dynamics at each activation cycle, the photo-activation time was limited to ~ 20 s and was followed by the acquisition of a 5 µm-sized apical image stack resulting in a total time resolution of 35 s. The basal surface of the anterior (left) half of the embryo was photo-activated. (B) All cells show pulsatile behavior. Graphs illustrate the area of three representative cells in each category (non-activated region: top; activated region with constricting cells: middle; activated region with non-constricting cells: bottom) over the course of one experiment. Yellow circles indicate the position of automatically identified local maxima used for further analyses. 