Let us try to know Nikola Tesla. This scientific genius, holder of about 300 patents, pioneered technology we take for granted today, was a man out of time. Not only a genius, but an insatiable searcher - his biggest legacy is his tendency to "fix things that aren't broken", opening up entire fields of research and experimentation in the process.
Personally, he would have been described as eccentric - OCD, a proponent of eugenics, and a lifelong celibate who avoided romance because it would interfere with his work. Very tall and extremely thin, he was a distinguished sort of handsome - many women fell in love with him over the years, but if he noticed, he didn't care.
Although he was a proponent of women's rights, believing that women will become the dominant gender in the future. He memorized entire books - once he read one work by an author, he then had to read that author's entire library.
He claimed to never have slept more than two hours at a time, spending all of his time isolated in his lab - with the exception of a nightly dinner at Delmonico's, from exactly 8pm to exactly 10pm. A complete history of his work would take volumes.
The man was a machine - in his early school years, a headmaster wrote to Tesla's father claiming that if Nikola were allowed to remain in school, he would work himself literally to death. Thankfully, that didn't happen, because where would we be without.
Tesla actually worked for Edison, hired to solve the lingering problems remaining on various projects, including direct-current electricity. He solved those problems and developed alternating current electrical power - using Edison's DC power, we would need power stations every square mile.
Tesla's AC power was better able to travel distances and could be more easily regulated, and he figured out how to transmit electrical power wirelessly. So how did Edison thank him for his hard work? By refusing him the large bonus (anywhere from $50,000 to 1 million dollars) he promised before the work commenced, and instead giving him an $8/week raise.
He was playing around trying to photograph Mark Twain using a particular type of gas discharge tube, but the only thing that showed up on the film was the camera's metal screw. His research notes and experimental data were lost, but he was inspired to return to the project a year later after hearing of William Roentgen's discovery of X-ray imaging.
He developed a higher-energy single-tube version of the X-ray machine, one that used no target electrode but produced a much stronger burst, powered by a Tesla coil. He was one of the first researchers to warn of the danger of continued or prolonged exposure to X-ray radiation, noticing skin lesions on his hands after using them as X-ray test subjects.
Much in keeping with his life so far, nobody believed it was controlled by invisible waves in the air, crediting telepathy, magic, or a trained monkey inside the boat instead.
Later, when Marconi sent the first radio transmission, Tesla famously said that it was done with 17 Tesla patents. He eventually sued Marconi over the patent infringement, and won - then it was overturned in Marconi's favor, then again overturned in Tesla's favor. But by this point, he was dead.
As ingrained as his reputation for genius is now, when he was alive, Tesla was considered a mad scientist. Some of his inventions, while fascinating, certainly border on cartoon-villain territory.
First, there was the "earthquake machine" that nearly brought down his apartment building and could possibly have cracked the Earth's crust. It was a simple oscillating device that he set to vibrate at exactly the same frequency as his building.
He frantically took a sledgehammer to it at the last-minute (right before police arrived) when he realized the extreme implications of such a device. Set to the oscillating frequency of the planet (which he also figured out, by the way), the device could cause total devastation and eliminate the human race.
He also invented a death ray, or at least he claimed to. There was no evidence of it found after his death, but he claimed it could generate enough force to bring down an entire enemy fleet from 200 miles and drop enemy soldiers in their tracks.
Sadly, this legend of a man died alone in a hotel in New York and was discovered by a maid two days later. His possessions were immediately seized by the government because it was thought that there might be something that shouldn't fall into enemy hands. After analysis, that was determined to not be the case - but gosh, he left us so much already.