Hands are two of the most important parts of the human body; we use them each and every day for hundreds of thousands of mundane and not-so-mundane tasks, like typing this article. But what if you grew up without hands? What if you couldn’t climb the monkey bars or hold a pencil or cut your own food with a fork and knife? Until now, you’d be out of luck. But doctors have proven that hands aren’t as irreplaceable as we once thought they were.

In a world's first, a child has received a double hand transplant. That’s right; not just one hand, but both.

Eight-year-old Zion Harvey has had a pretty rough life thus far. At age 2, a life-threatening bloodstream infection led to both his hands and feet being amputated. It also destroyed his kidneys. At 4 years old, he got a transplant from his mom, Pattie Ray. But at age 6, his mom found out about Shriner’s Hospital for Children in Philadelphia, which specializes in caring for kids like Zion that have prosthetics on their limbs. She also learned of a radical new procedure at the University of Pennsylvania that would give her son the hands he’d lost.

Only about 60 people worldwide have undergone upper extremity transplant surgery since 1998, including Penn’s first case, a young woman in 2011. But no child has received a single hand transplant, let alone both. "The doctor at Shriner's thought Zion would be a perfect candidate," Ray told the Philadelphia Inquirer. Zion was a suitable candidate because he was already taking antirejection drugs for his kidney transplant. These would help his body handle the newly attached hands as well.

The attachment of hands to arms that they didn't initially grow on is called complex composite tissue transplants. Doctors first have to attach blood vessels, then bones, then nerves, muscles and skin. What made the surgery even more complicated than usual was the fact that they were performing on an 8-year-old boy instead of a 38-year-old man.

On July 6, Zion and a team of 12 surgeons underwent an 11-hour procedure, which saw the team splitting up into four separate groups, all with their own priorities and responsibilities. Steel plates and screws secured the hands to Zion’s forearms, while the arteries and veins were sewn together with string thinner than human hair. In the documentary below, you can see the moment blood begins to flow into Zion’s new hands.

Zion now faces months of rehab, and it'll take up to two years for him gain feeling in his new hands. However, there has never been a more suitable boy for the task. So far, he has held a book, scratched his face, and shook hands.

"His maturity is way beyond his age, as is his insight and sensitivity," transplant team leader L. Scott Levin told the Inquirer. "He's brilliant, not just smart. And his stoicism has been remarkable. I've never seen him cry, complain of pain, or be withdrawn."