The evidence of creatures whose existence is uncertain is studied by cryptozoology, a science researching presumable proof of animals considered extinct or out of this world, which are still occasionally reported as seen in diverse locations. Such hypothetical creatures are usually referred as "cryptids", a term coined by John Wall in 1983, while cryptozoology is a term attributed to the Scottish adventurer and explorer Ivan T. Sanderson, the Father of cryptozoology is regarded as Bernard Heuvelmans, who published a book using this term for the fist time in 1955. Bernard Heuvelmans believed that cryptozoology would be undertaken with scientific rigor, but keeping an open-mind to find the grains of truth behind fantastic elements in folk tales depicting fantastic unseen creatures, and that folklore and traditions are the best sources to approach these myths.

William J. Broad wrote in the New York Times, "Monster lovers take heart. Scientists argue that so much of the planet remains unexplored that new surprises are sure to show up; if not legendary beasts like the Loch Ness monster or the dinosaur-like reptile 'Champ' said to inhabit Lake Champlain, then animals that in their own way may be even stranger. Cryptozoologists try to unveil the mystery behind hidden creatures which all of us have heard about, but just a few have been seen very briefly that it is impossible to determine where the truth ends, but usually is where the myth begins.

The Loch Ness monster (Nessie), Mothman, the Abominable Snowman, and Chupacabras, are just a few of those creatures whose existence is not clear, and there is not enough proof whether to confirm or deny the legitimacy of reports made by witnesses who have seen them. Skepticism is prevalent among scientists, despite the fact that many cryptozoologists are also respected scientists in other fields, who have found vestiges of previously unknown animals, but still cannot find the missing proof of creatures seen during the last two centuries.

Anyway, notable cryptozoologists have contributed actively with their research, including Bigfoot researchers Erik Beckjord, Peter Byrne, Ren