Cells in the notochord rudiment of a zebrafish embryo undergoing mediolateral intercalation to lengthen the forming notochord. BODIPY® FL C5-ceramide (Cat. No. D3521) localizes in the interstitial fluid of the zebrafish embryo and freely diffuses between cells, illuminating cell boundaries. This confocal image was obtained using a Bio-Rad MRC-600 microscope. Image contributed by Mark Cooper, University of Washington.