What we have here, really, is an "ORIGINS" moment of some future superhero or villain.
Maybe they're very young and in the sandbox... or maybe they're in their teens -- a typical time for such radical bodily changes...
Whatever is happening is new to the person it's happening to.
Perhaps the power has just appeared randomly, or as an after-effect of an alien abduction, or the young techie brain has just perfected her palm-beam gizmo, or - of course - maybe this is some emotionally-rooted physiological response to some external situation?
Character/Scene: YOUTH DISCOVERS THAT THEY CAN SHOOT ENERGY FROM THEIR HANDS