English: Embryonic development of the roundworm C. elegans from the 1-cell stage to the formation of a worm nearly ready to hatch. DIC microscopy, embryo is about 60 microns long. A living Caenorhabditis elegans (a model roundworm) embryo shown at various stages over 15 hours of development. The embryo starts at the 1-cell stage in the upper left, then 2-cell (center top), 4-cell (right top), 12-cell (2nd row, left), 26-cell early gastrulation (2nd row, center). A 558-cell worm is about to hatch out in the lower right. This is a single plane, by DIC microscopy. Nuclei appear as clear circles in the more granular cytoplasm