Whenever an animal dies at the San Diego Zoo, researchers take a sample of the animal's DNA, such as a bit of its eyeball or sperm and then freeze it in liquid nitrogen.

The Frozen Zoo has been active for the past 40 years and during that time it's gathered genetic information from over 10,000 individual animals and more than 1,000 subspecies and species.

Like Us on Facebook

The icy vials may someday even be used in experiments to resurrect recently extinct animals, like the Hawaiian Po'ouli bird. The stainless steel tanks hold the genetic material of these animals.

A rhino named Angalifu was 42 and he passed away in December 2014 from cancer. With his death, the total number of northern white rhinos dropped to only five. None of the rhinos in question are able to reproduce.

If new technology comes-up, scientists believe they'll be able to make a white rhino in about 10 years. The project received criticism, naturally. Critics asked about the feasibility of the project and if it's worth investing so much time and money to bring back a species such as the white rhino.

"Screwing around with science to save a white rhino might be fun and I would like to see it preserved and am all for biodiversity, but it's so far down the list of things we should be doing first," said Paul Ehrlich, a senior fellow at the Stanford Woods Institute for the Environment at Stanford University.

Currently, the only northern white left in the United States, 40-year-old Nola, munches on apples at the San Diego Safari Park. When she dies, there is talk of placing her in the Smithsonian so future generations can see a northern white rhino.

The Frozen Zoo has been successful in using its stored genetic material. Frozen sperm was used in the cloning process and for artificial insemination to reproduce the giant panda. Zoos all over the world are focusing more and more on preserving wildlife species for future generations.

TagsFrozen, animal extinction, White Rhino, rhino, Panda, extinct animals, DNA, genes, wildlife preservation