Video narration
How can you see a transparent, unstained microorganism without staining it? With the bright-field microscope you know, a transparent specimen can be hard to distinguish against the bright field. Dark-field microscopy, a type of light microscopy, reverses the view: the microorganism appears bright against a dark background. It isn't stained or glowing. The illumination changes. A dark-field condenser, the special light-directing part beneath the stage, contains a central opaque stop. It blocks direct central light, while the condenser directs light obliquely onto the specimen. Light scattered by the specimen enters the objective and forms the bright image. The setup also includes a light source, specimen slide, stage, objective lens, eyepiece, and focusing knobs. The familiar microscope parts remain; the key change is the illumination. That scattered light makes the unstained microorganism visible against darkness.