This is a special edition of nightline. Good evening. Youre about to witness an unforgettable encounter. Pat hartison, a firefighter badly bumped in the line of duty, endured the most extensive face transplant ever attempted. But his experimental surgery required a selfless act on the over a year later nancy millar is coming face to face with a man whose bravery led to this moment. Oh, lord. Take a deep breath. Reporter just up those stairs is a man nancy millar has never met. Whats going through your mind . Reporter but his face she already knows. Im going to try not to lose it. Reporter it belongs to pat hartison, the recipient of a groundbreaking face transplant. Theres no way to describe the thanks and the gratitude that i have. Reporter the donor, nancys son david. Tonight shes going to meet some of the people whose lives he saved and come face to face with pat for the very first time. Its going to be emotional on both ends. No more tears. Happy tears, happy tears, happy tears. Here i come. All right. Reporter its been more than david rodibagh. Come on, grab a couple of bouquets. We were really close. Almost like we were twins. Reporter she raised him as a single mother. Their tight bond forged while they traveled the country working together at craft fairs. He liked to create. He knew how to do just about everything. He had a serious, serious thing for speed. Ive been with fifth gear 12 years. Reporter his love for bicycles brought him to new york where he worked as a bike mechanic. Ive been riding my whole life, when i could walk my parents bought me a 9 why turtles huffy bike, started busting my eyes open and breaking bones and ive been doing it since. There was no fear in that boy at all. Reporter the group he rode with becoming much more than friends. Its like a family outside of a family. Everyone looks out for everyone. Of people. Reporter al lopez was one of them. Dave was without a doubt the best guy you never met. Reporter flying through the air, defying gravity, thats david ripping around the track at a red bullsponsored race in 2014. Youve got to gas it, not think about it. Just go, go, go. Dave was never supposed to die. You could never think about stuff like that if you were the type of dude that did the type of stuff that dave did. Reporter a year after winning that race, dave suffered a head injury in a bike accident while he wasnt wearing a helmet. After clinging to life for more than three weeks, nancy made the heartbreaking decision to let him go. But david would live on in the tiny mementos and the big memorials his friends set up and the countless people whose lives were about to change. This was all meant to be somehow. I think he knew he was going to be giving. Reporter dave had chosen to be an organ donor. And he was also a Perfect Match nearly 15 years in the making. An unprecedented procedure to give pat hartison a new face. The volunteer firefighter and father from mississippi ran into a burning house, searching for survivors, when the roof collapsed. You know, when i came back home i was a totally different person. Reporter he was lucky to survive but the fire robbed him of his scalp, ears and nose. His eyelids and lips were also gone. I think the first time i through was the first time i saw him. Reporter pats oldest daughter alison was just 6 at the time. I remember going up to the house. And my mom and stepdad literally had to drag me in the house. Because i was scared. Reporter while his devastated family and friends adjusted over time, pat never could. He became withdrawn, depressed. Doctors told him he would ultimately go blind. A second. Reporter desperation led him to dr. Eduardo rodriguez at nyus langon medical center. The pioneering surgeon in the emerging field of face transplants had been looking for the perfect patient, and pat was the one. The reality is we can make you much worse than you are now. If this were not to work, weve actually made you worse than you were before. So you completely understand this, right . Oh, yeah. Reporter willing to risk his its in gods hands. It will happen when hes ready for it to happen. Reporter the father of five well aware that his surgery would only be possible with another familys loss. I pray for them daily because i cannot imagine losing somebody at a young age and then having to be asked to give what theyre asking to give. Reporter it took two years to find the right donor. Nancy millars son david. But because face transplants are still experimental, they first i would donate his face i said, of course. And of course at the time i was thinking just parts of his face. And they said, no, we mean the whole face. And they looked at me and they i said, of course. I mean, no hesitation. It didnt matter. Reporter just two days later, pat is wheeled into surgery. It takes 12 hours donors face. Dr. Rodriguez disappears into patricks o. R. It will take him another 14 hours to complete this surgery. In the donors room another team of surgeons rushes in. There are other lives on the line. In operating rooms across the city, four other patients are being prepped for their own lifesaving operations. Among those saved on this day, desperately waiting for transplants. Every day 22 americans die waiting for a lifesaving transplant. Nationally only 50 of eligible adults are even registered as organ donors. We have a crisis here. We call it a crisis in the u. S. Reporter helen irving runs live on new york, a group that matches organ donors to patients in need. How many organs was david able to donate . Heart, liver, also donated bone and skin and corneas. Reporter the bone and tissue donations could have saved or improved the lives of up to 50 people, all from a single organ donor, david rodabagh. Its been over a year sincebeen here . Yeah. Reporter a tough year for nancy. While grieving her sons death she was also battling cancer. Now shes back in new york for the First Time Since he passed away. Do you feel him here . I do. He used to walk up behind me and put his big ape arms around me and just just sway back and forth and say, i love you, mommy. You were my life. You were my everything. He used to always bend over and kiss me on the forehead, and wed reciprocate, as soon as hed leave that last thing id do. Reporter tomorrow nancy is going to meet the people whose lives were afd david by daves organs, including pat. I want to kiss his forehead. Reporter the next morning a boils truss gro boisterous group of excited families meet nancy. How do you tell somebody youve never met that you love them . We just want to say thank you. Reporter one by one, they get that chance. Im nancy. How you been . Whats your name . Nicholas. You are gorgeous, look at you. Could i have a big hug . I have to say thank you. I have to let you know how much your decision has changed our life. Do you skateboard . Skate, rollerblade. You know i love you. And you dont even know me. Reporter three familie intertwined with nancys. They told me i wasnt going to get a heart. I wasnt going to give up. I said, it will come for me. Can i open it now . I would love to hear your heart. Oh my god. Press down. So strong. We would like to thank you once again for the wonderful that you guys will forever be in our hearts. God bless you. Reporter when we come back, pat hardisons 15month journey to say thank you. Hopefully shes not going to regret her decision of doing this. Reporter and the moment pat and nancy come facetoface. This is in many ways the big moment. Pats going to walk down the stairs. Whats going through your mind . Im ready. Reporter when nightne returns. Lly get in shape. Not to be focusing on my moderate to severe chronic plaque psoriasis. So i made a decision to talk to my dermatologist about humira. 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You and roomba, from irobot. my hero zero by lemonheads zero due at signing, and zero first months payment on select volkswagen models. This black friday at the volkswagen we met a mother heartbroken turning her tragedy into hope for another by donating her sons face. A year after that unprecedented transplant, shes now about to meet the courageous firefighter who received it. After more than a decade of standing out, his face scarred by fire a beautiful day. God has blessed us with a beautiful day. Reporter former fireman pat hardison is finally blending in. Im just a normal guy walking do t here we go. Reporter his first glimpse of this new reality just nine days after the most extensive face transplant ever performed. Just take a close look. Reporter looking in a mirror for the first time. An untap contractor face staring back. You see your hair growing . Reporter the outward signs of the pain and torment he lived with now gone. In the 15 months that followed he made an incredible recovery. And cheekbones. Im glad to meet you, you look fabulous. Reporter pats been back home in mississippi for a year. A dad in his 40s looking more like an elder brother with his new youthful face. Oh, im like a new man. Like a shiny brandnew penny. Reporter his eye doctor, who once warned him he was going blind, amazed at his progress. Smile at me, look ame he can do things that were never possible before all this happened. Come a long way. Thank you. Reporter but patricks transformation is much more than skin deep. Every day hes reclaiming pieces of his life that were lost in the fire. I was in a prison of my own home. Now im able to do everything that i wanted to do. He doesnt just sit at home anymore. He actually gets out and talks when i look into my kids eyes, i see happy innocence their eyes because they see how happy i am. Now were able to go on vacations. A small thing like go to a movie. Things i couldnt do before. Its a miracle. A godgiven miracle. How are you . Reporter this past summer, pat paid a visit to live on new york, the team who spent two years trying to find his donor. Thank you. Gratitude. They are full of awe. Whats it like having to try to shave again . Its a blessing to be able to do that. Maybe you can show them your new head of hair. Full hair. Thats full, just got it cut a couple days ago. Reporter with all the mesmerizingrogress hes made, theres still one person he has yet to thank, the donors she has had some very hard times. Im ready whenever shes ready. It will be a great day when i meet her. That looks perfect. Reporter now more than a year and a half later, nancy is finally ready. If my health was better, wed have done this a long time ago. Reporter her battle with cancer finally behind her. My eyelashes and eyebrows just came back. How are you feeling today . Good . A little nervous. Its going to be a very emotional day. Hopefully shes not going to regret okay. No more tears. Look up. Look at you. Look at him move slow down. Thank you for being so strong and so healthy. Thank you for risking your life to do this. When i knew you were a firefighter, i knew you had the strength to go through this. I had no hesitation. We got it done. Look at your face. Look at patricks face. Beautiful. You are beautiful. How do you feel . I feel great. He and i both have the same little scar right here. May i kiss your forehead if. Yeah. Reporter a poignant ritual between mother and son, now shared with patrick. Thank you. Thank you. May i look at you . Do you mind . I dont mind at all. Youve got his beauty mark. Youve got hair, look at this. The ears. Not as long as he kept it but its there. Do you have holes . My kids pick at me all the time about areaings. Now. No, son, daddy dont do earrings. Reporter the family man expanding his family. As proud of you as i was my own son. Thank you. And thank you for making it through all of this. My kids have a lot to do with that because its i wanted to see them grow up, wanted to see my daughters get married. Reporter living out every fathers wish. His legacy now forever intertwined with nancys. Youre a gift to us. Because youre able to to carry david on for us. Correct. Its not davids face, its your face. When i talked to dr. Rodriguez, i said, its patricks face, and tell him only happy tears. The best day of my life was the day david was born. This is the secondbest day of my life. Reporter the future is bright for these recipients. Are more than 100,000 people waiting for a lifesaving transplant. Waiting for their own donors. Someone like dave and nancy, whose courageous decisions gave others a second chance. When we come back what nancys doing now to honor her heres a little healthy advice. Take care of what makes you, you. Sturizing lotion with 5 vital nutrients for healthier looking skin in just one day. Aveeno . 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Com to honor her sons memory, nancy millar is launching the David Preston helmet society for helmet pat hardison is writing a book and planning to pursue a career as a motivational speaker. Before they met pat the firefighter had an unexpected honor for his donor. Every year at the end of the year we always nominate a fireman of the year, give them a plaque, name on the wall. This year everybody nominated david. Oh my lord. So we would like you to come, any way possible ill be there. He wanted to be a fireman so we wanted to do that. Well all be there in spirit. You can watch our original story on the groundbreaking face transplant on our Nightline Facebook page. Our profound thanks to pat and nancy, everyone at live on new york, and the team at langgold medical center. Thanks for watching abc news. Good night, america. Nye west mental collapse. Was he really handcuffed to a gurney. Gigi hadid apologies for her Melania Trump imitation