With the reinvigoration of Marvel in the 1960s under the leadership of Stan Lee and Jack Kirby, DC found itself a new and more potent competitor. Marvel succeeded by breaking what had become by then generic archetypes of superheroes by introducing characters which were younger and more flawed (and thus appeared more human and appealed to a younger crowd in a more direct manner.) After falling behind Marvel in sales, DC was finally forced to adopt much of the same system which Marvel had, by introducing such young teams as the Teen Titans to compete with the X-Men.