The Marvel Cinematic Universe was dealt a serious blow at the conclusion of Avengers: Endgame when Tony Stark sacrificed himself to defeat Thanos and save the universe. But while his demise shocked most of the MCU, there were some telling hints that his time was coming. The first was his willingness to sacrifice himself in 2012's Avengers, but in hindsight, the five years he got to have a family after Avengers: Infinity War was also an indicator. But one cleverly hidden hint came from the most unlikely of places -- his tech.

Tony was a futurist who would continue to innovate toward the future and always see the potential in advancing technology. And he best exemplified this through his armors. Using a box of scraps, Tony would find problems with his tech and create solutions. Perhaps the most obvious was his innovations with the Arc Reactor and more efficient ways to put on and take off his suit. But as the years progressed, he realized that having armor at the ready was the most important aspect.

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After Iron Man 3, Tony realized that his mind and physical capabilities made him Iron Man even without the suit. This newly formed symbiotic relationship with his armor would continue to inform future iterations, as he could now program a sentry mode and have multiple armors at the ready. But he still knew he could take things further, developing nanotechnology for his Mark 50 armor.

Much like the Mark 42, this armor was a prototype design to test his nanotech. But unlike the Mark 42, this armor was weapons-ready and was used to face Thanos. It would later be expanded further with the Mark 85 to have hard light shielding and a lightning rod to channel Thor's lighting for a power boost. But once Tony reached nanotech, there was no logical place for his technology to go, thus thematically sealing his fate.

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Tony Stark clicks his fingers wearing an Infinity Gauntlet

While Tony still helped to discover time travel and invent a way to travel through it, his true metric for innovation was his armor. He gave all of his engineering expertise to his suits, and his nanotechnology served as the pinnacle of that. So, while the grand debut of the Mark 50 was a sight to behold for audiences, it has now become a quiet acknowledgment that he had approached the end of the line with a suit design that couldn't expand further.

Tony's nanotech has yet to be seen again outside his armors and may not appear in future MCU projects. But it represented a man who could finally show that he and Iron Man were one entity. It was a second skin that he used to protect others, and he used it as such. However, in hindsight, it was clear in Avengers: Infinity War that the moment he could finally showcase his true self to the world, it would be the final gift he would have to give.