A single chromatophore expansion movement. A Naef stage XX embryo was dechorionated and embedded in a 1% agarose chamber filled with FSW and then placed under an upright microscope with DIC illumination at high amplification (40X). The movie is accelerated four times the normal speed and shows the expansion of a single chromatophore. As a stimulus to induce the movement, we turned on a fluorescence lamp with a rhodamine filter for a few seconds. Muscular fibers alternate in pulling the chromatophore from different directions; consequently, the pigment cell is unevenly stretched at the beginning. Nevertheless, the result is a fully expanded chromatophore by the end of the movie.