Now, Malaysian scientists are hoping to use tissues and cells from Iman and other dead rhinos to bring the population back.

The project, conducted by a team at the International Islamic University Malaysia (IIUM), focuses on stem cell technology and in-vitro fertilization. The process is similar to cloning technology, in that it aims to give birth to a new baby using cells from old rhinos, said Dr. Muhammad Lokman Bin Md. Isa, one of the lead researchers.

"Before the three rhinos (the last survivors in Malaysia) died, we got their cells, and the cells are still alive -- which is why I'm quite confident," Dr. Lokman told CNN. "If you don't have any cells, or if we just had tissue that aren't living anymore, we can't do anything with that. We can only put it in a book or museum. But now we have a living thing that we can use."

Here's how the process works: In collaboration with the Borneo Rhino Alliance (BORA), the researchers collected cells and tissue from the last three Sumatran rhinos at BORA's sanctuary -- including Iman -- before each died.

The cells came from the rhinos' hearts, lungs, brains and kidneys. Crucially, the team collected stem cells -- basically, raw material from which cells with specialized functions can be generated.

There are then two possible approaches. The first is to develop these stem cells into an egg and sperm, to create an embryo that will be implanted into a surrogate mother. The surrogate will likely be another rhino, either a Sumatran rhino from another country or another species.

The second method is to take the egg of a surrogate animal, remove the nucleus, and join it with a Sumatran rhino's somatic cell. This technique was famously used to clone Dolly the sheep in 1996.

Lokman and his colleagues are trying both ways.

Because the stem cells self-replicate, the team has a decent stockpile and can try different methods to see which works best.

The team is still in the preliminary stages; next, they need to analyze the cells to create a genomic database, differentiate the stem cells, and work with zoos and conservancies to find a suitable surrogate female. There are a number of ways this could go wrong; the fertilization could fail, and even if it doesn't, the pregnancy could fail once the embryo is implanted.

Iman died at BORA's Borneo Rhino Sanctuary last year, where she had been kept and cared for since her capture in 2014. She was 25, and had cancer, which was starting to cause her pain because a tumor was putting pressure on her bladder.

There are a number of factors that complicated these efforts; the female rhinos at the reserve turned out to be infertile, and plans to set up an international breeding collaboration ultimately failed due to "a series of incidents, some sociopolitical, some biological, and some simply bad luck," said Susie Ellis, executive director of the International Rhino Foundation, in a statement after Tam's death.

With Iman's death, the IRF declared the species extinct in the wild in Malaysia; the remaining rhinos are scattered across Indonesia and Thailand.

The population's decline was initially caused by poaching for their horns, which were coveted as ingredients in traditional Asian medicine. Later, it was exacerbated by fragmented habitats and human encroachment on the environment, which prevent the rhinos from gathering and breeding.

There are now only five remaining rhino species worldwide, and all are threatened. Some sub-species have already vanished; the western black rhino, native to western Africa, was declared extinct in 2013 due to poaching. The last male northern white rhino died last year, which is what pushed scientists to try in-vitro fertilization with Fatu and Najin.

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Every Sumatran rhino has died in Malaysia. Scientists want to bring them back with cloning technology - CNN