The most interesting room in the American Museum of Natural History is one you'll never see. Its inhabitants are millions of years old, its proprietors among the brightest in their field. This is the big bone room, home to what is arguably the largest and most important collection of mammal bones in the world. And we got a first-hand look.

When you think of the AMNH and its massive fossil collection, you invariably think of the fully formed skeletons that grace its exhibits. Don't. Only a small percentage of the museum's offerings are actually on display; the rest of what's arguably the largest and most important collection of ancient bones in the world resides in a separate 10-story building. And seven of those floors are all dino.

Inside the Bone Room: Where Dinosaurs Live at AMNH

The rest of the collection is kept in yet another room, hidden in the bowels of the museum on shelves that resemble the stacks of a library—one populated by the remains of some of the oldest mammals ever to walk the planet, the bones of which alone weigh several hundred pounds. A lot of these specimens, found in the latter part of the 19th century—back when paleontology first focused on large species displays—have huge historical importance. The whole operation is overseen by one man: Mark Norell.

Norell, the museum's chairman of the division of paleontology, recently invited Gizmodo inside to wander through the AMNH fossil library. But Norell probably requires his own introduction: He's one of the most important living paleontologists, and his job is the one you dreamed about having when you were a kid. He is responsible for discovering and naming three different dinos—the Apsaravis, the Byronosaurus, and the Achillonychus.

Inside the Bone Room: Where Dinosaurs Live at AMNH

When he's not in New York, Norell is traveling the world in search of new species. When he's back at the office, he works from an amazing octagonal tower occupying the top floor of the turret on the southeast corner of AMNH. Probably only four or five people in the world have access to it and, to get there, you have to walk through a series of hallways filled with locker after locker of species specimens shipped in from all over the world.

When we met Norell, he'd just returned from Mongolia, where the museum has an ongoing expedition to continue developing its ever-growing catalog of fossilized creatures. That's where the bone room comes in.

When you walk in the bone room, you are immediately dwarfed by the massive dinosaur bones, organized carefully on durable wheeled racks and heavy palettes. The bones are organized by species and the expedition on which they were discovered. There's a row for the Jurassic expedition to Colorado in the late 1800s, rows for the Gobi expedition of the 1990s, and more. On the back wall, half a dozen shelves keep about 50 individual vertebrae from a diplodocus unearthed in 1895. Hundreds of countries, hundreds of years, and hundreds of dinos are represented in just this one space.

Inside the Bone Room: Where Dinosaurs Live at AMNH

Some bones are as tiny as your own fingers, while others are hundreds and hundreds of pounds. There are giant skulls, massive leg bones, tiny samples of fossilized dinosaur skin, and bits of small tail bones. While some pieces can be handled as easily as a paperclip, others have to be moved with a forklift parked in the corner of the room.

Some of the bones sit on the shelves, intact, pieced together years and years ago by careful paleontologists. Some are still encased in the plaster jackets they arrived at the museum wearing, 10, 20, 30, maybe 100 years ago. Norell clarified that they don't necessarily know what everything is in the bone room, which means important discoveries about fossils still take place decades after the expeditions that find them.

Inside the Bone Room: Where Dinosaurs Live at AMNH

When bones come back to the museum from a dig, they don't come back as intact skeletons. Most of the time, a paleontologist will bring back a whole mass of dirt and rock that contains something they think is promising. These prehistoric segments of sediment, rock, bones, and eggs, are then carefully encased in plaster casts, and shipped to the AMNH in giant wooden crates. They might stay in these crates for years and years. So something that was actually found decades ago could be identified as a brand new species tomorrow.

In the meantime, they're carefully tucked away in the most amazing storage unit we've ever seen.

Inside the Bone Room: Where Dinosaurs Live at AMNH