Behind the scenes of Natural History Museum overhaul

>>> but the wear and tear of time left some of its most famous exhibits in need of a little repair. nbc's katy tur at at the museum where they are getting ready for a grand opening this weekend. good morning.

>> reporter: good morning, matt. thousands of people visit this museum every day and as you say the big draw is the north american hall of mammals where even in the 3-d imax world the displays still manage to lure you in. that being said been 70 years since the first display opened up. as anyone can attest time stops for no man or frozen animal, for that matter. it's not every day you see someone fluffing up a buffalo's hair or redyeing the coat of an eight-foot tall alaskan brown bear , but when faced with touching up the wild, it certainly does help if the animals are stuffed. inside these dioramas at the american museum of natural history , restorers got a chance to work in a world sealed off since the '40s, but while the animals stood still, time did not.

>> how faded were the bison? they are a deep rich brown right now, a caramel brown. what color when they before?

>> about like your hair.

>> reporter: exhibit lighting also faded the once lustrous fur of the jack rabbit , bleached the eye of the mountain goat and left the cougar looking a little tired. the hall was conceived in the 1930s , meant to give people a chance to explore the wild of north america , right smack in the middle of the concrete wild of new york city . famous for iconic scenes in books like " catcher in the rye " an movies like " night at the museum ." it's where childhood dreams come to life with that magical feeling of seeing something you're not supposed to see so close, so life-like. each animal started with a real skelton covered with exact molds of muscles and finished off with real fur. they are hailed as the greatest examples of taxidermy in the world, but even greatness needs some tlc.

>> it was just a general look of neglect, so what the museum decided to do was to find a way to bring them back, to make them look as beautiful as they did when they were first installed.

>> reporter: so they took out fish, replaced the mountain lion 's whiskers and cozied up to the wolves bringing life back to the majestic creatures and magic back to the museum. grand opening saturday, coinciding with the 154th birthday of the father of conservationism and the most popular guy around the museum.

>> theodore roosevelt , 26th president of these united states of america at your service.

>> i'm not sure of any other presidents who have been a scientist in the way that theodore roosevelt was. you're seeing many of the places in north america and many of the species that he wanted to protect.

>> that might be it.

>> moments frozen in time and preserved for generations to come. no doubt teddy would be proud. now the hall has been partially closed off for about a year and a half. the grand opening is tomorrow with a very big celebration. matt, it's your chance to come back here and see if it's as magical as you remember it when you were a kid.

>> i've been there a lot. one of the rainy day favorites in new york city . thanks very much. appreciate the