Check out a preview before the premiere on Sunday October 21, 9p et/pt Nat Geo revisits this classic film and so can you! Stream the classic film here.

Nat Geo took you through the aging process during Inside the Living Body, now it takes you on a ride through the human body to figure out what exactly all of our moving parts are doing. A showcase of the amazing "machines" that make up our bodies. Producer Chad Cohen took some time to detail what it was like to actually film inside the body.

Nat Geo: What makes this show different than other shows about the human body?

Chad Cohen: This program shows how the entire body works together as one very well-oiled machine. But we also highlight how the body sometimes doesn’t work, with stories of everyday people undergoing extraordinary new medical procedures. We feature the first study injecting stem cells into patients suffering from heart failure; the first test measuring a performer's vocal activity during a live performance; and the first retinal implant trial. We also show off a lot of new medical imagery. You’d be amazed at the places you can stick a camera these days.

Nat Geo: How were you able to get access to film Steven Tyler of Aerosmith from the inside out?

Chad Cohen: Steven had recently come to Dr. Steven Zeitels of Massachusetts General Hospital with a vocal bleed that had caused the band to cancel part of its tour. Dr. Zeitels pioneered a noninvasive method of laser surgery that zaps the blood vessels, sealing them off and stopping the bleeding. Steven was very impressed with the surgery and happy that his voice was working again. Both he and Dr. Zeitels were interested in getting the story of the technology out there, and I think they trusted National Geographic Channel to tell it in the way it should be told.

Nat Geo: What was it like filming the live sequence with Steven during the concert?

Chad Cohen: It was crazy backstage, not the sort of place a National Geographic producer usually finds himself. Steven was a pleasure to work with and was really interested in learning how his voice actually worked. The doctors hooked him up with devices to measure the speed of his vocal cords and to monitor his heart rate and respiration rate during the live performance. It was hilarious when he went out on stage and said, “Thank you to Massachusetts General Hospital and National Geographic for getting me ‘more wired’ than I have ever been before.” During the concert, we recorded how many times his vocal cords flapped together — it was more than 500,000 times, and his vocal cords traveled more than six miles over the course of the show. No one has ever recorded real-time data like that during a rock concert.

Nat Geo: Was it difficult to remain unobtrusive during the complex surgeries you filmed?

Chad Cohen: In an operating room, you hear these warning signs from the doctors and the nurses before you come in that everything on the blue table is sterile. If you bump this table with so much as a hip they will have to take everything off it, sterilize it and bring out a whole new table of equipment. That kind of gets you on your good behavior.

Nat Geo: What was your biggest challenge in making this program?

Chad Cohen: It was more of a personal challenge. We were looking for a new way to show chewing and digesting food … I somehow volunteered to be the patient! We found a very friendly gastroenterologist to send a six-foot-long endoscope through my nose and mouth and put a camera on the back of my tongue while I chewed salad. And taking it further, she sedated me and went all the way down through my esophagus to my stomach to show the acids, and then she poked through into my small intestine.

Nat Geo: What inspired you to take on this project?

Chad Cohen: We wanted to update National Geographic’s Incredible Human Machine program from 30 years ago. At the time, it was groundbreaking. Endoscopes were just coming out, so we were getting images of the body that we’d never seen before. In a lot of ways you just can’t find a more inspiring topic than the human body. We take it for granted all the time, but once in a while we need a little reminder that says, look at this, look at what we do and look at everything that’s going on inside us.

Nat Geo: How did you find the new technologies out there being tested and implemented?

Chad Cohen: We talked to dozens of doctors. It was ironic because every one would tell us that their focus of the body was the most important part. The eye doctor said it to me first, that without the eye you could never navigate through your day. The next one said the same thing about bones, that you wouldn’t have any structure for your body. From a larger context, you realize that they are all right, that each part is so fundamental, so it’s fascinating.

Nat Geo: Is there any one particular medical procedure that most impressed you?

Chad Cohen: With all the doctors we feature, each of whom has a very different specialty, the concentration is on harnessing the power of the body to heal itself, whether it is through stem cells or biologically engineered material. The heart bypass we featured used stem cells. The shoulder surgery used a very advanced biomaterial. In the future these same technologies could restore hearing or vision, even grow new nerves or repair spinal cord damage. The standard practice for years has been that if you have a tumor, doctors operate and take it out. If you have heart problems, they give you drugs. The new medicine is about getting the body to use its own repair and maintenance system to fix us. You can take stem cells from one area of the body, put them in another and they will potentially grow and heal an area that’s not working. Scientists will still say that they don’t know why it’s working … it just is. And it’s incredibly promising.

Nat Geo: What would you like viewers to take away from the program?

Chad Cohen: Genetically and on the inside, we are 99 percent the same. This show is able to give this amazing view of the body, so hopefully people realize how incredible every single one of us is.