Pepper could hear the AC/DC from the second she stepped out of the car. So, it was going to be additionally extra today. She hated these days. She couldn't imagine why, even Ironman hadn't been out last night. The whole house was echoing Back in Black, but it was loudest in the kitchen, where she found Tony in a tank top that at some point used to be black. Now it was green and yellow with dried spit up and hints of brown -

"Hey there Pepper! It's nice to have some spice in life!"

Pepper rolled her eyes at the lameness of it.

"A-are you drunk?"

"Drunk? No, I haven't the time to touch a bottle that wasn't for babies. I'm additionally sleep deprived. I'm Tim Drake sleep deprived, whatever that means. Does that mean anything to you, Pepper?"

He wasn't clearly in this universe!

Pepper sighed and stepped closer to talk to him.

"Right, and where's the girl?"

"Nah. No girls tonight. Y/n's sleeping in my room. Coffee?"

Tony drank the cup he had just offered Pepper a second ago.

"And you're supposed to hear her over all this noise?"

Tony took offense.

"AC/DC is not noise. It's classic music. And for your concern, I've rigged the baby monitor. If she cries, the music stops and her cries come through."

"Uhuh, and how long has she been sleeping?"

Tony swiped up a holographic clock.

"Three hours now." Tony said calmly.

"And she hasn't cried once!"

"Well she had a long night, she's bound to be passed out."

Pepper crossed her arms.

"Anthony Edward Stark!"

Tony dropped the cup in his hand and the music stopped at his command.

"Okay, fine! I'll go check on her."

Pepper walked Tony up to his bedroom, where baby Y/n lay in the middle of the bed with pillows at her sides, and a bunch of baby equipment thrown about the room.

"See, she's fine. Sleeping." Tony said from the door.

Pepper rolled her eyes and went to the sleeping baby. She stroked the baby's face but the baby didn't respond. She picked y/n up in her arms but again the baby didn't move.

"Tony, she's not responding." Pepper told with concern in her voice.

"Sh-she's sleeping." Tony said, trying to hold his calm.

Pepper took out y/n's hand from the wrap and put her thumb over the tiny wrist. Pepper immediately put her ear to the baby's chest and shouted.

"She's not breathing Tony!"

"Okay, time to go! JARVIS!"

An ironsuit flew in and Tony put y/n in a car seat, zipped up the front and flew off to the nearest hospital.

Pepper called up the best infant doctor she could reach as she drove to the hospital, and both Tony and the doctor were at the hospital before her.

Tony wanted to go in, but was held back by Pepper and a few other hospital staff members. Instead he paced back and forth and up and down till he was informed that Y/n was moved to a medical suite.

Tony ran up, expecting to see y/n playfully moving her arms and legs free from a constricting wrap. Instead, he found the room dimly lit, occupied with a glass incubator. Y/n lay still inside it, with a tube in her throat breathing for her. Tears fell on the glass as Tony grazed a hand over it, Pepper stood behind.

Doctor Marvel turned their attention to an x-ray screen.

"You see this line right here?"

"Yeah that's a blood vessel."

"Correct. But there's supposed to be two of them." The doctor paused to let the information settle.

"One's missing, and the baby-"

"Y/n," Tony sternly informed.

"Y/n isn't getting enough circulation to the lungs and other organs."

"W-what do you do?"

"In most cases I'd do an invasive operation, but seeing as she's too little... I'd recommend against it. I'm sorry."

Thankfully, an arc reactor was already keeping him alive, cause Tony's regular heart would have stopped beating. He hunched over the back of the couch, heaving, and Pepper tried to console him.

"The surgery itself is safe, but the invasion could cause-"

"Shut up." Tony whispered, but the doctor heard.

Doctor Marvel cleared his threat before speaking next.

"Piece of advice? You could do more for her than I ever could." With that statement, he took his leave.

Tony sat down on the couch and Pepper with him.

"Well, she is your daughter. You have a weak heart, she's got-"

"It's not just her lungs. She's not getting any blood. Her heart's beating fine, so I can't give her a reactor. And I CAN'T BUILD A FRICKIN' BLOOD VESSEL!" He stood as he shouted.

Baby y/n turned her head in her sleep, it was a small turn, but big enough for dad to notice. Tony walked over to the incubator and rested his head on the glass, stroking it as if his daughter.

"I'm sorry baby girl. I'm so sorry."

"What if it could build itself?" Pepper said and Tony looked up at her.

"What?"

"What if the blood vessel could build itself?"

"How the hell is that supposed to happen?" Tony angrily scoffed, brushing off the idea as silly.

Pepper pinched her nose.

"Okay, regular Tony Stark would have picked something out of what I said. You are emotionally driven and sleep deprived. Sleep, you're not helping Y/n awake." She ushered him back to the sofa and pushed him to sit, and Tony threw up his hands and laid down.

His sleep was short, but his dream was straight out of a tv show. He jumped out of the sofa and looked around for Pepper. When he didn't find her, Tony immediately began to plan out his idea. When Pepper came back in with a cup of hospital coffee in hand, the room was littered with every type of paper apparently available to the genius Tony Stark, and Pepper closed the door behind her with a knowing and proud smile.

"Welcome back, Tony Stark," Pepper whispered as she found Tony somewhere.

"N-no, don't step on that, that's... important." Tony said as he took a quick glance at where she was standing. He gave out a hand to her and led her somewhere clutter free, and then immediately twirled her in a hug.

"Whatever you did to me, thank you." He kissed her. "I thank you. Y/N thanks you." he rambled between kissing her head.

"Enough about me," Pepper playfully brushed, "What did you do?"

"Me? Oh nothing." But was Tony Stark a humble man? He walked away from Pepper and pulled up a screen on an arm piece of the Ironsuit.

"Just made nanotechnology a real thing," he popped up a screen showing what looked like tiny black white blood cells, that flickered with electricity once in a while.

"Nanotech? Isn't that years away?" Pepper was utterly shocked.

"Sure, but at the moment, my daughter doesn't have years. So I'm gonna bring the years to her." His English wasn't quite the best at the moment, but his science was literally years ahead of his time.

"Need some really tiny tools, and a science bro, and these babies are live!" He slammed a finger on the arm piece to make his point. "You could program them to do anything; rebuild bones, turn off the electricity, could be a mass weapon of mass destruction. But the only things these guys are gonna do, if and when they work, is save my daughter's life."

Pepper looked on like a teary eyed proud momma as Tony explained his science too complicated for any writer to write or a reader to understand.

Y/N had to stay at the hospital for the time, but the second Tony could bear to be away, he went to pick up his science bro, Bruce Banner. Their first stop was to the hospital where Tony introduced his daughter to his friend, and then they were away to the lab. With the genius of Tony Stark and Bruce Banner combined, and all the available prototypes existing in the world, nanotech became a thing of the present.

Crazy as he was, Tony wasn't going to use a first time tech on his baby girl right away, so when he wanted to test it, he found the perfect opportunity when JARVIS reminded him of his and Pepper's upcoming anniversary. First, Tony took Pepper to dinner, as Pepper had kindly allowed for him to skip presents this year because of how busy he was saving h̶i̶s̶ their daughter's life. Before going back home, they picked up stuffed toys and went to see Y/N in the hospital, who was doing better than that first night, but still very much in need of daddy's help.

After the hospital visit, Tony took Pepper home, where he finally showed her his best yet prototype of the nanites he and Bruce had come up with. To demonstrate he could task the little things with any act in the world, Tony showed Pepper a piece of raw diamond and asked her just how she would like it cut. What Pepper said, Tony programmed, and in the little glass box, the diamond apparently cut itself to the shape and style Pepper wanted.

"Incredible! It actually worked." Pepper said with excitement.

"Wait hold on! You can't really see it properly till it's up close!" Tony went ahead and opened the glass box and picked up the diamond with a diamond grabber.

"Let me see!" Pepper eagerly looked over Tony's shoulders but he pushed her away.

"Hold on a sec, give me space!" Pepper relented and stepped back a bit. "Okay, here have a look."

As he turned, Tony went down on his knee, and in his hand was the diamond, installed on a silver band he had created during his first run with Bruce. Pepper put her hands up in shock and out of the corners came Bruce Banner, holding baby Y/N in his arms.

"Well, nothing would've been possible without you, Pepper. So here's your due credit." Said Bruce.

"Pepper Virginia Potts. You have given me a heart and kept me alive for much too many times for me to count. But none of that matters to me, obviously. You helped me save my daughter's life, and I want you to keep doing that for the rest of your and our life. What do you say, will you be a part of my little, messed up world?"

Pepper pulled Tony up to his feet.

"Thanks for that. My knee was really starting to hurt." Duh, you can't expect consecutive emotion from Tony Stark without a self righteous statement somewhere.

"Tony Edwards Stark. I would love to be a part of your little, perfect, world!"

Tony slipped the ring on and they kissed to the applause from Bruce and JARVIS, and apparently Y/N who had woken up to witness her father's proposal. With an arm around Pepper, Tony went and grabbed his baby from her godfather's hands, and Bruce left the little messed up family to have their first day together alone. After all.