Drosophila sperm undergo incredible morphological changes during development to eventually produce some of the longest sperm in the animal kingdom at ~2mm (human sperm are ~50um). This image shows a young spermatid that just started out on this dramatic journey. The cell boundary is marked in blue and the nucleus of the cell is in white. From the nucleus extends the structural component of the sperm tail (green), which is wrapped by mitochondria (pink) that will eventually supply the sperm tail with the energy it needs to swim. Both this structural component and the mitochondria will elongate from the few micrometers they are in this image to almost 2mm in length over several days in a process that is critical for fertility.