Imagine a sealed-off world where humans must survive by growing their own food, recycling air and water, and relying only on their environment.
This is the world's largest Earth science experiment and it dates back to 1987.
The ambitious project spanning 7,200,000 cubic feet is called Biosphere 2.
But where is Biosphere 1, you ask?
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Well, that would be Earth.
The scientific research facility is located in Arizona, US and was designed to replicate Earth’s natural ecosystems (Biosphere 1) in a fully self-sustaining, enclosed environment.
Space Biospheres Ventures began construction of the current facility in 1986 with the goal of testing the feasibility of space colonisation by proving that humans could survive in a completely self-contained habitat.
Now, the facility is under the ownership of the University of Arizona.
In 1991, eight people - four men and four women - were sealed inside the facility with everything they needed to survive.
All their food, water and resources had to come from inside the biosphere and they were to have no contact with the outside world.
The project launch was staged like a space mission. The $150 million facility was flooded with media attention, with cameras rolling as the team in matching jumpsuits entered their new home for a planned two-year stay.
At first, everything seemed promising.
The biosphere came equipped with forests, deserts, laboratories, recycling systems, and even a coral reef.
It was also home to a variety of animals, including pigs, chickens, hummingbirds and bush babies, all of which were carefully selected to help sustain the enclosed ecosystem. However, things took a bad turn fast.
Oxygen levels plummeted so dangerously low that scientists had to pump in extra air to keep the crew safe. Meanwhile, food supplies ran short, forcing the biospherians to ration their meals, explained Linda Leigh, a participant who lived in Biosphere 2.
Understandably, morale was deteriorating among the crew, which eventually led them to split into two factions.
To make matters worse, all of this was going on in the public eye. Tourists would visit the habitat daily, tapping on the glass and taking pictures like it was a human zoo.
By the time the experiment was terminated, the team emerged exhausted and underweight - but very much alive.
To some, Biosphere 2 can be seen as a failure.
However, as one of the biospherians, Mark Nelson put it: "Just the fact that the same number of people came out as went in is a triumph.”
He added: “I like to say we built it not because we had the answers. We built it to find out what we didn’t know.”