English: A recording made on a laser scanning confocal microscope depicting one image plane. The paired dorsal aortae and the associated medial-most elements of the lateral vascular network are shown beginning at approximately HH13. The pseudo-colored green fluorescence denotes Tie1-YFP endothelial cells. Note that the endothelial cells that comprise the aortic tubes ‘slough-off’ and enter circulation. The newly dislodged cells tend to remain in close association with the luminal face of the aortic endothelium, reminiscent of leukocyte rolling behavior, before being swept away by blood flow. Other circulating Tie1-YFP endothelial cells appear to originate from lateral arteries feeding the aortae. These data demonstrate that circulating endothelial cells emerge from both aortic and arterial branch vessels. A confocal image frame was captured approximately every 11 mins or 5.4fph for 13 hrs. Mag bar  = 100 µm.