Photomicrograph of a typical endothelial cell colony-forming unit (CFU-EC) that is counted as an EPC.³⁴  The cluster of round cells sits on top of spindle-shaped adherent cells that emigrate from the base of the cell cluster. Over time, the cluster of cells disappears, leaving the adherent spindle-shaped cells that display features of endothelial cells. Phase-contrast image was collected using a Zeiss Axiovert 2 inverted microscope (Carl Zeiss, Thornwood, NY) with a 5 × CP-ACHROMAT/0.12 NA objective. Image was captured with a SPOT RT color camera (Diagnostic, Sterling Heights, MI).