Confocal scanning microscopy of CD41-GFP/LMO2-dsRed embryos. Shown are 2-dimensional photomicrographs of confocal microscopy near the trunk and caudal portion of an embryo 48 hpf. Two corresponding movies of 3-dimensional reconstructions of the same embryo are available as supplemental material on the Blood website; click on the Supplemental Movies link at the top of the online article. Of note is that the major vessels, whose endothelial cells are tagged with LMO2-dsRed, emit red fluorescence, and the nonmobile CD41-GFP⁺ cells emit green fluorescence. The GFP⁺ cells are extravascular and are clearly located in the region between the dorsal aorta and the posterior cardinal vein (trunk view, arrow) and caudal portion between the caudal dorsal aorta and caudal vein (caudal view, arrow). DA indicates dorsal aorta; PCV, posterior cardinal vein; ISV, intersomitic vessel; YE, yolk extension; and CV, caudal vein.