SCOTTSDALE: Time and death are "on pause" for some people in Scottsdale, Arizona.

Inside tanks filled with liquid nitrogen are the bodies and heads of 199 humans who opted to be cryopreserved in hopes of being revived in the future when science has advanced beyond what it is capable of today. Many of the "patients," as Alcor Life Extension Foundation calls them, were terminally ill with cancer, ALS or other diseases with no present-day cure.

Matheryn Naovaratpong, a Thai girl with brain cancer, is the youngest person to be cryopreserved, at the age of 2 in 2015.

"Both her parents were doctors and she had multiple brain surgeries and nothing worked, unfortunately. So they contacted us," said Max More, chief executive of Alcor, a nonprofit which claims to be the world leader in cryonics.

Bitcoin pioneer Hal Finney, another Alcor patient, had his body cryopreserved after death from ALS in 2014.

The cryopreservation process begins after a person is declared legally dead. Blood and other fluids are removed from the patient's body and replaced with chemicals designed to prevent the formation of damaging ice crystals. Vitrified at extremely cold temperatures, Alcor patients are then placed in tanks at the Arizona facility "for as long as it takes for technology to catch up," More said.

The minimum cost is $200,000 for a body and $80,000 for the brain alone. Most of Alcor's almost 1,400 living "members" pay by making the company the beneficiary of life insurance policies equal to the cost, More said.

More's wife Natasha Vita-More likens the process to taking a trip to the future.

"The disease or injury cured or fixed, and the person has a new body cloned or a whole body prosthetic or their body reanimated and (can) meet up with their friends again," she said.

Many medical professionals disagree, said Arthur Caplan, who heads the medical ethics division at New York University's Grossman School of Medicine.

"This notion of freezing ourselves into the future is pretty science fiction and it's naive," he said. "The only group... getting excited about the possibility are people who specialize in studying the distant future or people who have a stake in wanting you to pay the money to do it."