So what that means is when a protein folds or unfolds, it doesn't actually follow a precisely defined pathway, but it follows a partially defined pathway. And what that means is when the protein, let's say, unfolds, it goes from a very stable native state into a less stable state that has its own energy into a higher energy state. So this is even less stable than this and finally into this final state that is less stable than either one of these states. And so when the protein either folds or unfolds, it does so cooperatively. And that's why we have the Sigmoidal curve. And not only that, but it has to pass through these intermediate structures to actually get to that final structure.