Life through the lens
Introduction: Zebrafish
The zebrafish, Danio rerio, breeds year-round and produces hundreds of clear-shelled eggs with the developing embryo easily visible inside. The embryos develop from one cell to a swimming fish in about two days. The visibility and speed of zebrafish embryonic development allow scientists to observe the growth of organs in very young embryos.

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Still Image:
Closeup of a zebrafish eye
The cornea and retina are clearly visible in this image of a 3-day-old zebrafish’s eye (Danio rerio).
A three-day-old zebrafish embryo was mounted in fresh water between a slide and coverslip using a silicon spacer. The image was taken on an inverted compound microscope using a 20x DIC objective and digital camera.