Eobard Thawne is Flash's greatest enemy. Living in the 25th century, he was fascinated with the Flash and was his #1 fan, though at that time, Barry was long gone. Eobard wanted to meet Barry in person by going back in time. He went to a Flash antique shop and killed the clerk in order to steal the Cosmic Treadmill, a treadmill that if he ran on, he would travel through time. He miscalculated and actually traveled to the Flash Museum a couple years after Barry's death. He learned that he was destined to become a great enemy of the Flash. This drove him crazy. He went through the chemical process that gave Barry his powers and gained super speed. Eobard made a suit and named himself Reverse-Flash. He went back in time to kill Barry's mother in order to defeat the Flash. Barry's father got blamed, and he went to jail. Years later, Flash met the Reverse-Flash, and the two became bitter enemies ever since.