Why? Well, because in stage two we basically want to produce two identical three carbon molecules. And to produce those two identical three carbon molecules, we have to have symmetry in our molecules. So this is not symmetric, but this is symmetric. And so the glucose six phosphate is transformed into fructose six phosphate to make sure we get those two identical three carbon molecules in stage two. So you might ask, well if I keep this molecule in the glucose six phosphate stage, what will happen in stage two?