As one of the few pioneering female chemists in the 1960s, Stephanie Kwolek invented the flexible, tougher than steel fibers that were used to create life-saving body armor for law enforcement and soldiers. Kwolek died this week at the age of 90, her co-workers at DuPont, the chemical company where Kwolek worked, confirmed to ABC News. "She leaves a wonderful legacy of thousands of lives saved and countless injuries prevented by products made possible by her discovery," DuPont CEO Ellen Kullman said in a statement.