English: 1= 2P microscopy of forming dorsal aortae from stage 11 through 12 (longitudinal view). The time-lapse was acquired by Zeiss 510 META NLO as following: Objective: EC plan-Neofluar 20×/0.5, Chameleon: 900 nm (17.9%), Z-stack size: 111 um (3 um interval), Imaging cycle: 7.5 min, Total duration: 6.5 hours. Bright signals in the midline are non-specific excitation of yolk by the 2P excitation. Movie corresponds with data in Figure 5. Bottom. 4D EC tracking of the dorsal and ventral walls of the dorsal aortae (longitudinal view). Dorsal and ventral wall endothelial cells are indicated by orange and cyan, respectively. Movie corresponds with data in Figure 5.