Meet Sue. That’s the nickname of the most complete and best-preserved Tyrannosaurus rex skeleton ever discovered. Paleontologists, or fossil experts, found more than 90 percent of its bones in 1990.

Since 2000, the dinosaur has been on display in the main hall of the Field Museum in Chicago, Illinois. Millions of people have marveled at the fearsome predator. Now, Sue is on the move to a new exhibit on the museum’s second floor. The exhibit will open next year and will feature the dinosaur in a recreation of its prehistoric environment.

Sue lived 67 million years ago. Fossil remains are one of the few ways scientists can learn about long-extinct creatures such as Sue. Thanks to new techniques for studying bones, scientists are still learning new things about dinosaurs today. Museum workers will use this knowledge to reposition Sue’s skeleton so it is more accurate.

“It’s really exciting to move Sue and to be able to make these changes,” says Bill Simpson, a paleontologist at the Field Museum.

Meet Sue. That’s the nickname of a Tyrannosaurus rex skeleton. It’s the most complete one ever discovered. It’s also the best-preserved. Paleontologists, or fossil experts, found Sue in 1990. They dug up more than 90 percent of its bones!

The dinosaur has been on display since 2000. It stood in the main hall of the Field Museum in Chicago, Illinois. Millions of people have come to see the giant predator. Now, Sue is on the move. It’s getting a new exhibit on the second floor of the museum. The exhibit will open next year. The dinosaur will stand in a model of its ancient environment.

Sue lived 67 million years ago. Dinosaurs like Sue have been extinct for a long time. Fossil remains are one of the few ways scientists can learn about them. Scientists are now finding new ways to study ancient bones. That means they can still learn new things about dinosaurs today. Museum workers will use this knowledge to move Sue’s skeleton. They’re changing the position of its to make it more accurate.

“It’s really exciting to move Sue and to be able to make these changes,” says Bill Simpson. He’s a paleontologist at the Field Museum.

Sue is named after Sue Hendrickson, a paleontologist who noticed the dinosaur bones in a South Dakota cliff and dug them out. With the help of donations, the Field Museum paid $8.4 million for Sue at an auction in 1997. That’s the most ever paid for a fossil at an auction.

Once the museum received the skeleton, the staff got to work. People spent 30,000 hours removing the rock from the bones. Sue was “remarkably well preserved,” says Simpson. Scientists think this is because the dinosaur died near a riverbed and was buried quickly by mud.

A professional dinosaur assembler put Sue together in New Jersey based on the understanding at the time. Then the heavy, fragile bones were mounted with steel.

But as scientists learned more about dinosaurs, they realized Sue needed a change.

Sue is named after Sue Hendrickson. She’s the paleontologist who found the dinosaur bones in a South Dakota cliff. Hendrickson dug out the fossils. They went on sale at an auction in 1997. The Field Museum collected donations to pay for the skeleton. It bought Sue for $8.4 million. That’s the most ever paid for a fossil at an auction.

The museum received the skeleton soon after. The staff got to work right away. People spent 30,000 hours removing rock that was stuck to Sue’s bones. Sue was “remarkably well preserved,” says Simpson. Scientists think this is because the dinosaur died near a river. Flowing water quickly buried the skeleton in mud. 

A professional dinosaur assembler put Sue together in New Jersey. The body position was based on what scientists thought was right at the time. Sue’s bones were heavy and extremely fragile. The assembler mounted them on steel bars to hold them up.

Over the years, scientists learned more about dinosaurs. They realized Sue needed a change.

Moving a 3,500-pound skeleton is no easy task. Sue has more than 400 bones. The smallest—a tiny bone in the spine—weighs less than half a pound. The largest—a hip bone—weighs 314 pounds. Every bone needs to be removed from its mount and put back together.

When Sue is reassembled, the skeleton will get a few major upgrades. First, a set of rib-like bones called gastralia will be added to the dino’s belly. The museum has three-fourths of these bones but ran out of time to mount them the first time.

Sue’s skeleton weighs 3,500 pounds. Moving it is no easy task. Sue has more than 400 bones. The smallest is a tiny bone in the spine. It weighs less than half a pound. The largest, a hip bone, weighs 314 pounds. Every bone needs to be removed from its mount before moving the skeleton. Then workers need to put the whole thing back together.

When Sue is rebuilt, the skeleton will get a few upgrades. First, a set of rib-like bones will be added to the dino’s belly. These bones are called gastralia. Three-fourths of them are stored at the museum. But the assemblers ran out of time to mount them the first time.

Second, scientists will replace a plastic model wishbone with the real thing. Most meat-eating dinosaurs, including T. rex, have wishbones (like birds which descended from dinosaurs). Sue’s wishbone did not have symmetry, so scientists didn’t recognize it at first and didn’t know where to put it.

Since Sue’s first assembly, paleontologists have learned that other adult T. rex skeletons have similar wishbones. “We realized we had the correct bone all along,” says Simpson. Scientists will replace the plastic model wishbone with the real one.

Lastly, Simpson’s team will change Sue’s crouching position to a more upright one. This is how scientists now believe a T. rex probably stood.

The second improvement is to Sue’s wishbone. Most meat-eating dinosaurs, including T. rex, have wishbones. So do birds, which descended from dinosaurs. But Sue’s wishbone did not have symmetry like a bird’s does. Scientists didn’t recognize it at first. They kept the bone in storage. They gave Sue a plastic model wishbone instead.

Paleontologists have studied more T. rex skeletons since Sue was first assembled. They learned that those dinosaurs have similar wishbones. “We realized we had the correct bone all along,” says Simpson. Scientists will now replace the plastic model with the real bone.

Lastly, Simpson’s team will change Sue’s position. Instead of crouching, the dino will stand slightly more upright. This is how scientists now believe a T. rex probably stood.

When Sue was alive, South Dakota was hot, humid, and covered by forests. T. rex lived alongside other dinosaurs, like Triceratops and the duck-billed Edmontosaurus.

The new exhibit will take up an entire wing on the second floor. It will include the new Sue and teach visitors about this prehistoric ecosystem.

Simpson can’t wait to see it all. “We’re finally finishing Sue after all this time,” he says.

When Sue was alive, South Dakota looked very different. It was hot, muggy, and covered by forests. T. rex lived there alongside other dinosaurs. Triceratops and the duck-billed Edmontosaurus also wandered the land.

The new exhibit will be on the second floor of the museum. It will take up an entire wing of the building. Sue will be the star attraction. The exhibit will also teach visitors about the ancient ecosystem where Sue lived.

Simpson can’t wait to see it all. “We’re finally finishing Sue after all this time,” he says.