The field of xenobiology, or exobiology as some call it, began on Earth during the Twenty-first century. After the discovery of simple lifeforms in the Sol sytem, it became its own independent disciline and expanded as Terrans began exploring extrasolar worlds.
When Mars was surveyed in the first quarter of the twenty-first century, it was science's first detailed look at extraterrestrial life. Although the life there was dead, it laid the foundations for this field. After the Jovian expeditions, it became very clear that there was an abundance of life, throughout the solar system. By the time the first probe made its journey to the Alpha Centauri system, the fourth planet provided science with the knowledge that sophisticated life lived elsewhere in the galaxy. It was there that creatures similar to those on Earth were found. As exploration continued, scientist discovered new life forms in virtually every nook and cranny.
On Earth, species are categorized into invertebrates, mammals, reptiles, insects, arthropods, fish or birds. These families are also found on other planets along with new families like the binnerpods, fellites, and flits. On many worlds, these new creatures have already been domesticated as pets and livestock.
Today, xenobiology is still an exciting field. Scientists speculate that there could be several million unidentified life forms on the many unexplorerd planets. Researchers have established nearly a thousand facilities throughout Terran space to discover and study new life forms.