Denver, Colorado - What did you do for summer vacation? Three pre-teen dinosaur aficionados have the answer of a lifetime: they discovered the remains of a rare juvenile Tyrannosaurus rex in the North Dakota dirt.

Scientists and filmmakers announced Tuesday that brothers Liam and Jessie Fisher, ages seven and ten at the time of the find, and their nine-year-old cousin Kaiden Madsen were walking in the Hell Creek formation of the Badlands in July 2022 when they found a large fossilized leg bone.

"Dad asked, 'What is this?' and Jessin said, 'That's a dinosaur!'" exclaimed young Liam on a video call with his brother, cousin, father Sam Fisher, dinosaur experts, and reporters.

They snapped a pic and sent it to a family friend, vertebrate paleontologist Tyler Lyson of the Denver Museum of Nature & Science, according to a statement.

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When Lyson eventually arrived at the site, he brushed off a tooth and quickly realized the enormity of what the fossil hunters uncovered: an "extremely rare" juvenile T-Rex specimen that lived 67 million years ago – and could offer critical clues about how the king of dinosaurs grew up.

"It still gives me goosebumps," Lyson recalled on the call.

Kaiden's reaction to learning it was a T-Rex? "This is pretty cool, I can't believe we just found this."

The fossilized bones were excavated, placed in giant plaster jackets, and lifted by a Black Hawk helicopter onto a truck. They were taken to the Denver Museum of Nature & Science, where the public can soon follow progress on the fossil's preparation in a new discovery lab.

Rather remarkably, the saga is only emerging now, after a documentary crew and renowned scientists coordinated in secret over nearly two years with top natural history museums to present the kids' discovery.

Paleontologists estimate the "Teen Rex" weighed about 3,500 pounds, measured 25 feet from nose to tail, and stood about 10 feet tall – some two-thirds the size of a full-grown adult. It was believed to be 13-15 years old when it died.

"It's remarkable to consider how T. rex might have grown from a kitten-sized hatchling into the 40-foot, 8,000-pound adult predator we are familiar with," Thomas Holtz, a vertebrate paleontologist from the University of Maryland and a renowned T-Rex authority, said in the statement.

A documentary about the discovery debuts June 21 and will roll out to 100 cities in IMAX, 3D, and other formats.

"This is the kind of story that documentary filmmakers dream of capturing," co-director David Clark said in the statement.

As for the kids, Liam and cousin Kaiden said they'll remain amateur dinosaur sleuths, combing the Badlands for new discoveries.

But Jessin is looking to become a full-time paleontologist.

"It's been a lifelong dream of mine – probably because I've seen the Jurassic Park movie, and finding this T-Rex fossil," he said.

Meanwhile, Jessin offered sage advice for his fellow youths: "Put down their electronics and just go out hiking."