For example, in 2011 scientists from the SCRIPPS Institute in La JOLLA (USA) created the first stem cells of the extinct Northern white rhinos and endangered species of baboons-drylaw using samples of their frozen tissues.
"We will start with a pure southern white rhino embryo in the next weeks and months to test the system, and after that is successful we will implant a northern white rhino into a surrogate mother".
Researchers have created embryos from frozen white rhino sperm and eggs from their cousins the southern white rhino, another sub-species that has had its own remarkable bounce-back from the brink of extinction.
European biologists have created the first hybrid embryo of the extinct white Rhino, combining their sperm and egg from meeting their usual African relatives.
A caregiver calms Sudan, the last known male of the northern white rhinoceros subspecies, on December 5, 2016, at the Ol Pejeta conservancy in Laikipia County - at the foot of Mount Kenya - that is home to the planet's last-three northern white rhinoceros.
Cesare Galli of the Italian animal assisted reproduction firm Avantea, who worked with Hildebrandt, said there had originally been strong opposition from some conservationists to "interfering in nature" by using IVF or other lab techniques to save the northern white rhino.
Fatu is one of two remaining northern white rhinos, both female, who live on a nature reserve in Kenya.
An worldwide team of zoologists, veterinarians and other researchers plucked unfertilized eggs from southern white rhinoceroses, a closely related subspecies with a population of about 20,000.
Even with the rhino put under anaesthetic, the procedure is very risky because there is a crucial artery right near the ovaries, and it could cause the rhino to bleed out if punctured. "But I am afraid it is very much Nero fiddling after Rome is burning with respect to (northern) white rhino".
In 1960, roughly 2,000 northern white rhinos roamed central Africa.
Embryonic stem cell lines, which have been produced with the southern white rhino, provide another option.
They are the world's most endangered animals, with just two females left.
As more species slide towards extinction, the use of assisted reproductive technologies as a conservation mechanism has entered the spotlight.
Although the hybrid embryos mark a promising first step in restoring the southern rhinos' northern counterpart, scientists warn that the birth of a hybrid calf-already an ambitious goal- will not be enough to ensure the species' survival. The embryos developed to the blastocyst stage, which increases the chances of pregnancy after implantation into a surrogate female.
Eventually, the fertilized cells would be implanted into a southern white rhino surrogate, according to the scientists. They, therefore, injected each egg with sperm from animals that died years ago and applied electrical current pulses to trigger the fusion of the egg and the sperm. Hildebrandt said that the induction of sperm and eggs from northern white rhino's blood or skin cells could take a decade. "It was slaughtered by criminals which went for the horn because the horn costs more than gold". "We should come at it with everything we've got", Roth said. We can not afford to adopt a cavalier attitude toward extinction, as though animals were something to bring back at our leisure, he said.