Thats about it - why does the nuclear fusion release energy when fusing lighter elements, but absorbs energy for heavier elements? Something to do with the week nuclear forces low range and after Fe it simply crosses that range? But... every hadron in the nucleon has the week force, with its limited range, ... Or that the week force doesn't add up (limited range) while EM does? But in that case what does make it all "stick", why does giving more energy make it stick? .. waiting some answers, so I can get clearer on what questions to ask.