Nikola Tesla was a genius, and Thomas Edison "employed" Tesla on promise of payment later. After performing lots of research, fixing his machines, and garnering several patents which Edison stole from him, Tesla asked for his payment to which Edison said "you don't understand our American humor", at which point he stiffed Tesla and they ended their partnership. Edison used Tesla to pad his own pockets, stole his ideas, published them as his own, and then sent him packing with nary a dime to show for it, hence making him one of the sleaziest scumbags in history. That among many other things, which you can read at the link below if you're interested in a really entertaining comic presentation...it's definitely worth the read! I have to re-read it every time I hear anything about Tesla.
sorry for the long reply, he's one of my heroes (i'm an electrical guy, Thparky, get it? lol)