He was a physician who trained at Harvard University.
He served as a Navy SEAL.
Now he is set to become the first Korean-American to join a NASA mission in space.
The 35-year-old started his career as a seaman recruit after graduating from Santa Monica High School in 2002.
"I didn't like the person I was growing up to become," Kim said in a 2017 profile in the Harvard Gazette about his decision to enlist. "I needed to find myself and my identity. And for me, getting out of my comfort zone, getting away from the people I grew up with, and finding adventure, that was my odyssey, and it was the best decision I ever made."
As a member of SEAL Team 3, he served as a combat medic, sniper, navigator and point man on more than 100 combat operations across two deployments to the Middle East.
His duty led him to his next career.
Kim told the Gazette about a wounded comrade: "He had a pretty grave wound to the face. It was one of the worst feelings of helplessness. There wasn't much I could do, just make sure his bleeding wasn't obstructing his airway, making sure he was positioned well. He needed a surgeon. He needed a physician, and I did eventually get him to one, but ... that feeling of helplessness was very profound for me."
In 2012, he earned a bachelor's degree in mathematics at University of San Diego. He earned a medical degree in 2016 at Harvard Medical School.
One year into a four-year residency at Massachusetts General Hospital he was selected as a NASA astronaut candidate.
Out of more than 18,300 applicants, only Kim and 11 other Americans were selected for the 2017 class.
Training started in 2017, and he graduated the program last Friday.
“A true privilege and honor to walk among the @NASA Astronaut Corps with my brothers and sisters. We know there are many qualified and deserving candidates out there - we're the lucky ones to represent humanity. Let's work towards a better future for our world and our children,” he tweeted on Monday.
"I'm excited for the adventure," Kim told the Gazette in 2017. "I think it'll be another occupation where I say, 'I can't believe I'm getting paid for doing this.'"