The Frozen Zoo houses more than 1,000 species, but if you visit, you won’t see elephants or monkeys roaming about their enclosures. Instead you’ll see test tubes filled with cell cultures, stored in tubs of liquid nitrogen. All told, the samples take up slightly less space than a refrigerator. While the stored DNA is currently mostly used for research, conservationists hope it could one day be used to rebuild the populations of endangered species, or resurrect those that have gone extinct.

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The Frozen Zoo is run by the San Diego Zoo’s Institute for Conservation Research, housing genetic material from nearly 10,000 individual animals – some still alive, others long dead. A set of matching tanks houses a copy of the samples in a second, undisclosed location – just in case something happens to the originals. The samples in the Frozen Zoo come from institutions all over the world, including the San Diego Zoo and Safari Park. No animals are harmed during the collection process, which occurs either during routine health exams, or after the animal has died.

The collection dates back to the 1970s, when UC San Diego pathologist and geneticist Dr. Kurt Benirschke began collecting frozen cells and reproductive material for the zoo’s recently-formed Center for Reproduction of Endangered Species. At the time, scientists had no way of knowing that the first example successful animal cloning was only two decades away. In that time, the Frozen Zoo has managed to accumulate perhaps the world’s largest collection of stem cells.

Related: Researchers successfully splice woolly mammoth DNA into elephant cells

While no extinct animals have been resurrected yet, the zoo already has an impressive list of accomplishments under its belt. The stored materials have been used to inseminate San Deigo’s beloved giant panda, Bai Yun, and the scientists at the facility are hard at work sequencing the DNA of animals ranging from African elephants to two-toed sloths. One high-tech project even involves using stem cell technology to revive populations of the endangered northern white rhino. In the coming years, projects like this may help turn back what some scientists are calling the world’s sixth mass extinction.

Via GQ

Images via Franco Pecchio and playlight55