The first 90 minutes of sea urchin embryo development. Nuclei are visible as “thumbprints” in each cell. Microtubules are faintly visible just prior to and during mitosis.
Sea urchin eggs were fertilized, then immediately mounted in seawater between a slide and coverslip (using a silicon spacer). Images were taken at room temperature on a compound inverted microscope using a 40x DIC objective and digital camera.