This shows different z-plane images of a cluster of CTCs (from patient #1), which stained positive for M markers (red) and weakly positive for E markers (green) at time point 8. Fluorescent images were merged with DIC images. Nuclei were stained with DAPI (blue). This video relates to a paper that appeared in the Feb. 1, 2013, issue of Science, published by AAAS. The paper, by Min Yu at Massachusetts General Hospital Cancer Center in Charlestown, Mass., and colleagues was titled, "Circulating Breast Tumor Cells Exhibit Dynamic Changes in Epithelial and Mesenchymal Composition."