The storm over Manhattan beat against the glass ribs of Stark Industries, thunder pulsing through the power lines like a second heartbeat.
Inside the medical wing, machines whined, lights flickered, and Howard Stark paced a groove into the sterile white floor.
Maria's hand crushed his fingers. "You keep pacing and you'll wear a hole clear through to the prototype lab," she said between breaths.
Howard's smile was paper-thin. "Pacing keeps the mind sharp."
"Then sharpen it somewhere else."
The attending doctor looked at the monitor, frowned, and murmured to the nurse, "Every sensor just died. We've lost the heart trace."
Howard spun toward him. "What do you mean, lost?"
"I mean the child doesn't have one—"
The next flash of lightning showed it: a faint blue glow beneath Maria's ribs, pulsing in rhythm with her breath. The light grew brighter, steady, deliberate. When the infant came, the room went silent except for that hum—low, metallic, warm. Not a heartbeat. A reactor.
Howard stared. The baby's chest shimmered where skin met something else, a perfect silver ring that gave off gentle light.
Maria reached for the child. "He's breathing," she whispered. "That's all that matters."
Howard's voice shook. "He was born with a machine for a heart."
At the back of the room Edward Jarvis, the family's butler and bodyguard, took one step forward and bowed his head.
"Congratulations, sir. Madam. And welcome, young master. The world will adjust to you soon enough."
Maria laughed softly, even through exhaustion. "He hums."
Howard's eyes softened. "Then the world just found a new note."
By the time Tony Stark was four, the hum had become the background music of the house. He glowed faintly whenever he was excited, and he was excited about everything.
Dr. Evelyn Ross, the family physician, held a scanner over his chest.
"The energy field is stable, but the patterns are getting complex. He's not just generating power—he's learning from it."
Howard stood behind her with a tablet full of readouts. "He's creating self-regulating circuits. His body's building the first living reactor."
Maria crouched beside the exam table. "Does that make him sick?"
Ross smiled. "It makes him extraordinary."
"Cool," Tony said, staring at the blue hologram of his own energy web. "So my quirk is… me?"
Howard ruffled his hair. "Exactly. You're the blueprint and the builder."
Ross typed the classification. "Mutation type, full integration. Quirk name: Extremis."
Howard raised an eyebrow. "Latin?"
"The farthest point," Ross said. "Because that's what he is."
Howard built a regulator bracelet that night—a polished band that pulsed in rhythm with Tony's chest. "It'll help you balance your energy until you're old enough to do it yourself."
Tony tapped it, mesmerised. "It matches my heart."
Howard smiled. "It is your heart."
The mansion garage smelled of oil, ozone, and guitar riffs. Howard's vintage cars lined the walls like sleeping dragons. Tony wandered among them with a wrench in one hand and safety goggles sliding down his nose.
"Engines breathe," Howard explained, bent over a Ford Roadster's open hood. "The carburetor mixes air and fuel so the car can live."
Tony peered in. "Then this one's got asthma."
Howard barked a laugh. "Then we'll give it better lungs."
From the corner, AC/DC's Back in Black thundered through an overworked speaker. Tony nodded in time, legs swinging, eyes bright. Maria appeared at the top of the stairs, arms folded. "Howard Anthony Stark, is that my four-year-old listening to that?"
Howard shrugged. "He learns better with rhythm."
"Try lullabies."
"Too slow for science."
Even Jarvis smiled from the doorway. "Madam, I believe the young master has discovered his tempo."
When Tony was eight, the family jet touched down in Wakanda. The mountains shimmered behind invisible shields; the air smelled of rain and metal. King T'Chaka met them with quiet dignity, Queen Ramonda with grace, and beside them stood a boy Tony's age—Prince T'Challa, curious and serious all at once.
Howard and T'Chaka shook hands. "Vibranium for technology," the king said. "Each strengthening the other."
In the royal lab, while the men spoke of energy grids and containment fields, the boys drifted toward a workbench piled with scraps of metal.
"You build?" T'Challa asked.
"Every day," Tony said. "My dad says I was born with tools in my hands."
"My father says I was born with responsibility in mine."
"Sounds heavy."
They both laughed. Tony picked up a coin of vibranium. It sang faintly against his skin; his chest glowed in reply. "It's alive," he whispered.
"It remembers," T'Challa said.
Later, at dinner, Tony pulled a silver device from his pocket. "Wanna hear something better than the drums?"
He pressed play. Back in Black burst from the speaker. The two boys started bobbing their heads, laughing.
Across the table, Howard and T'Chaka were already chuckling; Maria and Ramonda exchanged identical exasperated looks.
"Your son's energy is contagious," Ramonda murmured.
Maria sighed. "So is the volume."
Howard raised his glass. "Let them be loud. They're the sound of tomorrow."
Back in New York, Howard hired Professor Hikari Sato, a quirk specialist, to teach Tony control. The woman's voice was calm enough to still hurricanes. "You don't fight the energy," she told him. "You listen to it."
Every morning they meditated; every afternoon Howard joined them with blueprints spread across the table. Science lessons and quirk lessons became the same thing. Tony learned to modulate the glow of his reactor by breathing in rhythm, to let the current flow like a song instead of an explosion.
Within months he could dim and brighten at will.
Sato arrived one day carrying small metal ingots—steel, titanium, vibranium. "Today we see how far your quirk can mimic the world."
Tony touched each sample in turn. His skin shimmered, matching color and density. When he reached the vibranium, the room filled with a soft hum that resonated in his bones. For a heartbeat his whole arm gleamed silver-blue.
Howard stared at the readings. "He's copying atomic structure."
Sato whispered, "He's becoming his inventions."
That night Tony dreamed of shapes—plates sliding over his skin, light weaving into armor. When he woke, he went straight to the lab and, without tools, called the materials back into being. Energy wrapped around him like liquid metal, solidifying into the first rough Iron Man suit.
Howard stood frozen. "You made armor out of yourself."
Tony grinned behind the glowing mask. "I told you my body is the suit."
The armor dissolved when he exhaled, light fading to skin. Howard's throat tightened. "You just built the future."
Weeks later, Tony wandered into his father's lab at midnight. Howard was hunched over the Stark Tower reactor design, frowning at cascading error codes.
"Your equations are off," Tony said, climbing onto a stool.
Howard didn't look up. "Go back to bed, kiddo."
Tony studied the hologram. "You're over-feeding the tertiary coils. Three microseconds off."
Howard blinked. "And your fix?"
Tony's reactor brightened. Without touching a thing, lines of code began to rewrite themselves, smoothing into symmetry. The thermal load flattened; the simulation cooled. Tony's voice stayed calm. "I made it listen to itself. Circuits shouldn't be forced—they should flow."
Howard watched in stunned silence as the final warning faded from red to blue.
"You just corrected a city's power grid."
Tony yawned. "Then make it pretty. Let the lights pulse like a heartbeat. People'll feel safe."
Howard smiled. "Done."
When Tony finally shuffled off to bed, the engineer saved the file under a new name:
PRIMARY_HB_01.tny — Heartbeat 01.
Time accelerated after that. The Stark complex became a city of ideas.
Montage:
– In gleaming labs, Howard and Tony built micro-reactors for hospitals—tiny hearts that powered prosthetics and stabilized unstable quirks.
– In testing bays, heroes tried on Stark-made gear that bent with their abilities: flame-proof gloves for fire quirks, sonic-dampening boots for speedsters, pressure-venting suits for explosion types.
– Energy grids across the world lit with blue light; cities ran on clean power.
– The Hero Commission signed contracts for HeroFibres™, Tony's adaptive fabric woven with arc-reactor nanites that learned a hero's rhythm.
Howard watched his son explaining the tech to a crowd of engineers. "Every thread listens to its wearer," Tony said. "Because power should never be louder than the person using it."
Maria stood beside Howard, pride shining in her eyes. "He's turning your legacy into a lifeline."
Howard whispered, "No—he's building his own."
One evening, father and son stood on the balcony of the completed Stark Tower. Below them, New York glowed with soft reactor light. The building itself pulsed once every few seconds—slow, steady, alive.
"When I was your age," Howard said, "I wanted to be the smartest man alive."
"And now?" Tony asked.
"Now I just want to keep up with my son."
Tony laughed. "You think Mom will let me put a lab in my room?"
"She already said no."
"Then we'll build one in the basement."
Howard chuckled. "That's my boy."
The wind carried distant music—AC/DC, faint through the city noise—and for a moment the tower's glow seemed to pulse in time with it.
Down in the streets, people looked up and thought the light was decorative. Howard knew better.
It was a heartbeat.
The first heartbeat of a world his son was already building.