X-Ray Vision is a superpower held mainly by Kryptonians, Daxamites and Martians. It is an ability which allows the user to see through most solid objects at will, with the exception of lead. The physical process by which this amazing vision power occurs is a mystery. Although it seems that the Kryptonian actually emits X-rays from his or her eyes, there has been evidence against this, as well. This power is likely attributed to the Photonucleic Effect, meaning that Kryptonians and Daxamites can only use the ability in the presence of a yellow star.
Martians - Martians can see through any object with no exceptions.
Kryptonians - Kryptonians can see through any object with the exception of lead.
Daxamites - Daxamites can see through any object with the exception of lead.