Superman (1939). Certain materials such as lead can block his X-ray vision. Superman can project beams of heat from his eyes which are hot enough to melt steel. He first used this power in "Superman" #59 (1949) by applying his X-ray vision at its highest intensity. In later stories, this ability is simply called "heat vision". Superman can hear sounds that are too faint for a human to hear, and at frequencies outside the human hearing range. This ability is introduced in "Action Comics" #11 (1939). "Action Comics" #1 (1938) explained that Superman's strength was common to all Kryptonians because they
Superman Universe, which is a shared universe of superhero characters owned by DC Comics, and consequently he frequently appears in stories alongside the likes of Batman, Wonder Woman, and others. Superman has sold more comic books over his lifetime than any other American superhero character. Exact sales figures for the early decades of Superman comic books are hard to find because, like most publishers at the time, DC Comics concealed this data to deny competitors, but sales of "Action Comics" and "Superman" probably peaked in the mid-1940s and thereafter steadily declined as part of a general trend in comic book sales.