I was just wondering that when we have a molecule, and you introduce heat, the molecule starts to get translation, rotation and vibration energy. I'm considering just a molecule with two atoms and one axis which binds them together. Now the real question is that why is there only two axis in rotation energy? Can't you have three axis there? I mean that you can rotate in the x, y and z direction. And yes, I do know that the third one is parallel with the axis which binds the atoms together, but can't you still make it rotate? I do realize that if the molecule is NOT symmetrical in that axis THEN it sure is considered a third axis on which the molecule can rotate. But even when it is symmetrical can't you pump energy in it? On a macroscopic level I do see that when you make something like that rotate around it's own axis it doens't "change" when you look at it, but it STILL can have energy on that rotational axis, which rose this question in my mind. I hope my explanation makes any sense, thanks for your answers! Thanks.