In collaboration with others at Marvel—particularly co-plotters and artists Jack Kirby and Steve Ditko—he co-created iconic characters, including Spider-Man, the X-Men, Iron Man, Thor, the Hulk, Ant-Man, the Wasp, the Fantastic Four, Black Panther, Daredevil, Doctor Strange, the Scarlet Witch, and Black Widow. These and other characters' introductions in the 1960s pioneered a more naturalistic approach in superhero comics. In the 1970s, Lee challenged the restrictions of the Comics Code Authority, indirectly leading to changes in its policies. In the 1980s, he pursued the development of Marvel properties in other media, with mixed results.