And so the beginning point of step three is this three phosphaglycerate molecule. And so that's what we have shown on the board. Now, this is carbon one, carbon two and carbon three. And what happens in this reaction is an enzyme known as phosphoglycerate mutase, basically catalyzes the movement, the transfer of the phosphoryl group shown in blue from the third carbon onto this second carbon here. And so we go from three phosphaglycerate, two two phosphoglycerates. Now we'll talk about why that happens in just a moment.