A video depicting the microcirculation as observed by intravital microscopy of a wild-type NOD/SCID mouse injected with fluorescently labeled human CD34+ cells can be downloaded at http://www.mssm.edu/labs/frenette/bone_marrow.shtml. One large collecting venule and a network of sinusoids can be seen. Free-flowing cells circulate rapidly in the field of view, while rolling cells move slowly on the endothelium of the BM. In the second sequence, two cells have become firmly adherent on the vessel wall and one rolling cell will arrest momentarily and then will be released into the circulation.