Guppies are among the most well-known and popular aquarium fish in the world, alongside goldfish. These live-bearing toothcarps can be admired in any pet store. Additionally, guppies have been introduced to countless subtropical and tropical waters outside their natural range, making them "global players" among fish today. Most people associate guppies with bright, eye-catching colors and large fins. However, those who delve deeper into the world of guppies soon realize that these gems offer many more fascinating attributes. Since their initial import, countless dedicated aquarists and guppy breeders, as well as many renowned biologists, have extensively studied guppies. Especially in the last thirty years, much has been learned about them.