Viewers in tears as cosmonaut who spent full year in space explains what he missed most about Earth

An astronaut who spent a entire year in space revealed what he missed the most about Earth in an emotional video.

Russian cosmonaut Mikhail Kornienko lived on the International Space Station from March 2015 to 2016. He and his crew mates were 'guinea pigs,' sent away to learn what long stints in space does to the body.

The now-64-year-old said he requested some particular items to be sent to space to make the mission easier.

Mikhail's profound view of the world sparked an emotional reaction from viewers online.

In a National Geographic video which has been viewed more than six million times, he explained that being in an enclosed space 'for a long time' created some 'rather stressful conditions'.

Mikhail Kornienko revealed what he missed most about time on Earth after a year in space (Bill Ingalls/NASA via Getty Images)

On returning to Earth, he said: "Some time needs to go by here on Earth, so I have not breathed enough of Earth yet.

"For me, everyday is a plus. A joy, you know? But the time comes when you adapt and you come back to normal, and you can begin to miss space as well."

Mikhail appreciated viewing Earth's natural beauty from above, describing what he noticed. He said: "There are many beautiful places. The Aurora [Borealis] is very impressive... Cities are also very beautiful."

But he soon realized one major issue while living in space, explaining: "There is a shortage of greenery, for real, like not enough forest... People need to understand this and psychologists somehow need to develop a set of measures for people who will fly farther."

The astronaut's profound words about the Earth left viewers in tears (KIRILL KUDRYAVTSEV/AFP via Getty Images)

To combat the lack of greenery, he made a special request for the resupply vessel: "When I flew, I asked the psychologists to send with the resupply ship simply pictures of Earth.

"Just views of nature: forests, rivers, little bitch trees, mountains. I hung all of this around the module, so the flight would be more joyful. You grab onto it with your gaze, look at the little birch tree and things get easier."

Overcome with emotion, viewers took to the YouTube comments to share their thoughts on Mikhail's experience.

One admitted: "I almost cry when he finally landed on earth and breath the air of earth after a very long time, It makes me emotional I dont know why."

A second said: "'Look at the little birch tree, and things get easier', cried little bit... people are awesome, earth is awesome."

A third said: "I'm a bit teary watching this" as a fourth wrote: "This was a great piece. I cried for the beauty of existence and humanity."

Another summed it up: "What did he miss? Everything. What did he experience? Everything."