Kryptonian Physiology

Why Kryptonians gain powers under a yellow sun, and why Superboy's are limited.

Kryptonians, the race from the planet Krypton in DC Comics, look human but differ greatly in physiology. Their cells absorb solar energy; under Krypton's red star their abilities match a human's, but under a young yellow star like Earth's Sun they gain powers such as super-strength, speed, invulnerability, flight, X-ray and heat vision. In some continuities their DNA is too complex for human science to clone easily.

Background

In Young Justice, Superboy is a hybrid human-Kryptonian clone whose human DNA holds back his Superman-like abilities; Lex Luthor's patches unlock his full Kryptonian powers for about an hour, at the cost of more aggression. Cadmus's fully Kryptonian clone Match becomes mentally unstable because of the difficulty of cloning Kryptonian DNA. In the fourth season, Jon Kent, the son of Superman and Lois Lane, is hinted to be developing Kryptonian powers.