After Harvey Dent was cought in an explosion of chemicles half of his face was damaged. However his face was not the only thing that was damaged. His mind was damaged as well. Because his mind was damaged by the explosion he could not make decisions for himself and had to rely on a double faced coin to help him make decisions. If the coin landed on the unscared side Two-Face would not comit any crime. If it landed on the scared side he would comit crimes. When Two-Face fliped his coin to decide if he was going to kill Rupert Thorne, Batman threw other coins at him which caused Two-Face to lose track of his own coin. Another time Batman swiched Two-Face's coin with one that would always land on its edge. Two-Face almost died trying to get it to land on one side. Another time Two-Face tied Batman to a giant penny. While Two-Face was not looking Batman took it from him and used its sharp edge to cut himself free.