Tempered Glass Rivet Gun Safety Elevators Automatic Fire Sprinklers 
Answer: Safety Elevators
There are a lot of hurdles to overcome when building an enormously tall structure. Among the many considerations, like structural integrity, utility distribution, and so on, there’s one very practical consideration: how to get people to the tippy-top of your building without forcing them to climb a thousand flights of stairs.
Long before incredibly tall “skyscrapers” appeared on city skylines in the early 20th century, one man solved that “people moving” problem. Elisha Otis didn’t invent the idea of an elevator or mechanical lift, but he did invent something we now take for granted: the safety brake. While contemplating installing a lift in the factory he worked at, he was dismayed to find how unsafe they were. He felt that it simply wasn’t worth the increase in efficiency around the factory if the lift could fail and send him or his fellow workers plummeting to their death.
In response to that, he and his sons invented a braking mechanism that would engage if the hoist ropes failed, preventing the lift from falling more than a few inches before locking into place (becoming the first safety elevator). At the time, he thought very little of his invention. He neither patented it, tried to sell it, or even requested a bonus for it from his superiors at the factory.
It wasn’t until his work at the factory ended that he decided to focus on his invention and launched a modest elevator company (named Union Elevator Works at first, then renamed Otis Brothers & Co. later). He demonstrated his invention at the 1854 New York World’s Fair and the public was absolutely amazed by his crowd-drawing demonstrations that involved Otis standing on an open lift and an axeman cutting the ropes. Suddenly, elevators weren’t a death trap waiting in the wings, but a perfectly safe and practical device that made constructing taller buildings practical.
That modest elevator company, as you can imagine, took off, and today Otis brand elevators are found all over the world (and in high profile locations like the Eiffel Tower, the Empire State Building, and the Burj Khalifa).