It has the organic component known as protoporphy that contains the carbon atoms, the nitrogen atoms, the hydrogen atoms and the oxygen atoms. And this entire region, shown in black, is the protoporphine. It's the organic component of that Hen group. Now, at the center of that protoporphinen is an inorganic atom, a metal atom, the iron atom. And this is what makes up the inorganic component of that Hen group. And it's this fe atom that is actually responsible to not only binding to the protein, but also to binding to that oxygen, as we'll see in just a moment.