The guppy also known as the millionfish, is one of the most popular freshwater aquarium fish species in the world. It is a small member of the Poeciliidae

Poeciliidae

Poeciliidae is a family of fresh-water fish which are live-bearing aquarium fish . They belong to the order Cyprinodontiformes, tooth-carps, and include well-known aquarium fish such as the guppy, molly, platy, and swordtail...

 family [females 4–6 cm (1.6–2.4 ) long, males 2.5–3.5 cm (0.984251968503937–1.4 ) long] and like all other members of the family, is live-bearing

Live-bearing aquarium fish

Live-bearing aquarium fish, often simply called livebearers, are fish that retain the eggs inside the body and give birth to live, free-swimming young.-Common aquarium livebearers:...

.
Robert John Lechmere Guppy

Robert John Lechmere Guppy

Robert John Lechmere Guppy was a British-born naturalist after whom the guppy is named...

 discovered this tiny fish in Trinidad

Trinidad

Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...

 in 1866, and the fish was named Girardinus guppii in his honour by Albert Günther later that year.