Movie 4

Cell-shape changes during Drosophila axis elongation. Wild-type embryo expressing Spider:GFP. Time indicated in min:s, images acquired every 15 s. Anterior left, ventral down. Cells are color-coded based on their width-to-height ratio (smoothed over a seven-frame window). Dorsal-ventral (vertically) elongated cells in red and anterior-posterior (horizontally) elongated cells in blue. More opaque colors indicate a greater degree of elongation.