We're taught not to judge a book by its cover, and we also shouldn't judge a fish by its size. This is the case for the humble zebrafish (Danio rerio), a fish so named for the distinctive stripes on its belly. Though the fish doesn't get much bigger than the size of your thumb, what we've learned from this fish is immeasurable.
As vertebrates, zebrafish have about 25,790 protein-coding genes (by estimates via ensemble.org), of which around 70 percent are related to genes found in humans. Of note, by the latest count, zebrafish seem to have more genes than humans - the protein-coding gene count for us is at 20,441.
Genetic similarity aside, biologists value zebrafish because of their transparent embryos, which serve as windows for different developmental stages. Zebrafish also have fast generation time and large brood sizes, which makes them cheap, fast, and efficient model organisms. Watch the video to learn more about how the discoveries made possible with the help of these tiny fish.