Developing eye of a zebrafish (Danio rerio) embryo, confocal light micrograph. The tissues have been stained with fluorescent dyes and illuminated with a laser. Individual cells (yellow) can be seen dividing. The lens is stained blue (centre). The zebrafish embryo is widely studied by developmental biologists because it is transparent. A confocal microscope detects light only from the focal point of its objective lens. By moving the focal point, sharp images of thin sections of an intact specimen can be obtained.