I know that water can be superheated, but my question is more fundamental. What causes water to boil at 100 deg C? I know that there are several factors (atmospheric pressure, nucleation sites, hydrogen bonding, surface tension, etc) but that's not what I'm getting at. I'm interested in the more fundamental reason as to why water boils at the temperature that it does (why a boiling solution doesn't exceed its boiling point). I'm not sure if I'm making sense as some people will probably tell me that I just answered my own question, but idk, why can't one "input" more energy into the system and cause water to boil at a higher temperature than 100 deg C?