Astronauts on the International Space Station have revealed a deceptively simple achievement: they got outer space's first flower to bloom.

Astronaut Scott Kelly, who took over the troubled experiment in December, triumphantly tweeted on Sunday a photo of the zinnia flower he painstakingly brought to life.

"First ever flower grown in space makes its debut! #SpaceFlower#zinnia#YearInSpace," the American wrote.

Astronauts have long studied plant growth in space in order in the hopes of better understanding how we might one day sustain human life on other worlds.

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But, as Kelly showed, it hasn't always been easy.

According to a NASA press release, the Veggie plant growth facility was installed on the orbiting lab in May 2014. The first test crop was red romaine lettuce.

“We lost two plants due to drought stress in the first grow out and thus were very vigilant with respect to the second crop,” said Trent Smith, Veggie project manager.

Our plants aren't looking too good. Would be a problem on Mars. I'm going to have to channel my inner Mark Watney. pic.twitter.com/m30bwCKA3w — Scott Kelly (@StationCDRKelly) December 27, 2015

The next batch was harvested successfully over the summer, and a NASA photo even shows astronauts Scott Kelly and Kjell Lindgren taking a bite of their crop.

The flowers, though, proved to be a tougher endeavor by far.

“The zinnia plant is very different from lettuce," said Smith. “It is more sensitive to environmental parameters and light characteristics. It has a longer growth duration between 60 and 80 days. Thus, it is a more difficult plant to grow, and allowing it to flower, along with the longer growth duration, makes it a good precursor to a tomato plant."

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Unfortunately for the zinnias, zero gravity proved itself to be a tough medium for flowers. Some of the plants died as a result of over saturation with water and mold growth.

When fans were used to help keep the plants dry, they proved so strong that the zinnias dried out.

Eventually, though, space got its first flower.

“While the plants haven’t grown perfectly,” Dr. Gioia Massa said, “I think we have gained a lot from this, and we are learning both more about plants and fluids and also how better to operate between ground and station. Regardless of final flowering outcome we will have gained a lot.”

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