A look at many of the more than 22,000 species of fish, from freshwater, to the deep ocean, to the colorful coral reef. We look at the origin of fish, how they breathe, why they have scales, and how ...

They don’t just detect drugs, bombs, and cancers—dogs can sniff out the amoeba-size larvae of invasive mussels and highly endangered flowers hidden in fields. Tule, a six-year-old Belgian Malinois ...