He was the father of the modern electric age & single-handedly created many of its wonders that we take for granted now-
Tesla was the inventor of A/C electricity, florescent light bulbs, wireless signal transmission, and other ideas that literally changed the entire world.
Unfortunately, he hasn't historically always received the credit he deserves & his efforts were often challenged or outright squashed by greedy corporatists like Thomas Edison, or short-sighted financiers like J.P. Morgan. Tesla initially worked for Edison, who screwed him out of compensation he owed for Tesla's inventions.
Before his success lighting the 1893 Chicago World's Fair with A/C power, he even had to find work digging ditches in New York City for a time after he left Edison's lab.
This History channel documentary, "Mad Electricity,"is an excellent overview of the amazing insight & accomplishments of this visionary mind.
Here's another great page on the PBS site for information about Tesla:
Tesla: Master of Lightning
Even his previously fantastical vision of wireless electric power is now finally being realized, as well.
Tesla was truly a genius & his work should be taught in every science class around the world.
“When wireless is perfectly applied the whole earth will be converted into a huge brain, which in fact it is, all things being particles of a real and rhythmic whole. We shall be able to communicate with one another instantly, irrespective of distance. Not only this, but through television and telephony we shall see and hear one another as perfectly as though we were face to face, despite intervening distances of thousands of miles; and the instruments through which we shall be able to do his will be amazingly simple compared with our present telephone. A man will be able to carry one in his vest pocket.”