Endothelial progenitor cells are cultured on nanotopographic substrates with a line-grating geometry and respond to these substrates through aligned and elongated morphology, reduced proliferation, and increased migration relative to flat substrates. The cells also form supercellular band structures, which lead to enhanced capillary tube formation upon the addition of matrigel. These results suggest that substrate nanotopography can be used to create organized vascular structures in vitro. Image taken at 250 x magnification.