MICHEL DELARUE, ISM / SCIENCE PHOTO LIBRARY MICHEL DELARUE, ISM / SCIENCE PHOTO LIBRARY
Sea urchin embryo, 16-cell stage, light micrograph. These 16 identical cells (blastomeres) have resulted from four phases of cell division (mitosis): the fertilised egg divided into two cells, then each divided again to form four, and so on. The sea urchin has long been used as a model organism in reproductive biology. This is a phase contrast image.
Model release not required. Property release not required.