And so if we draw a line, this will be a mirror image of this molecule. And so these oh groups, which point to this side, will point onto the opposite side on this molecule here. And so in the deisomer, we see that this green hydroxyl group, which is the hydroxyl group that is found on the stereogenic carbon, that is far less away from this aldehyde group. This is the carbon that we have to worry about. And if this hydroxyl group on the final stereogenic carbon points to the right side, then that is the deisomer, the Dnamer. But if it points to the left side, so that is called the L monosaccharide, in this case, the L erythros.