What kind of rays caused the Fantastic Four to mutate?

What kind of rays caused the Fantastic Four to mutate? Cosmic radiation was responsible for the creation of the Fantastic Four on Reed Richards’ fateful space flight. Lack of sufficient shielding caused Reed Richards, Sue Storm, Johnny Storm, and Ben Grimm to receive exposure to cosmic rays in space. This led to lifelong mutagenic changes in the four.

Cosmic radiation was responsible for the creation of the Fantastic Four on Reed Richards’ fateful space flight. Lack of sufficient shielding caused Reed Richards, Sue Storm, Johnny Storm, and Ben Grimm to receive exposure to cosmic rays in space. This led to lifelong mutagenic changes in the four.