Add that up. I would have to look at the same situation here, take all these, add them up for this one and then I would sum them together. And that would be my total or my internal energy. Now, if I had billions of molecules, I would have to do it for every single molecule. Now, one last thing I want to mention is that internal energy is a state function. And what that means is simply that eternal energy does not depend on the process or the pathway taken to get to this system.