Movie shows restricted distribution of PECAM-1[high] CD45+ cells to the luminal surface of the aortic endothelium from an E11.5 mouse embryo. PECAM-1[high] cells are in red, CD45+ cells are in green and the PECAM-1[high] CD45+ cells, defined as hematopoietic stem cells, can be seen in yellow. PECAM-1[high] CD45+ cells are scattered on the floor of the luminal surface, but not in subendothelial mesenchymal layers. Z-stack through whole-mount preparation of ventral aorta (150 images captured at 1.0 micron optical intervals) can be turned to allow clear observation of PECAM-1[high] CD45+ cells. Movie is Supporting Information Movie 1 and images from Z-stack are included in Fig 4 from Taoudi et al.