So RNH two where the other H atom basically came from, this group here, this is the thing that produces that colored product. And so as this reaction takes place, the oscillation reaction takes place very, very quickly and that's why we have a fast initial birth stage. And as this is produced, this creates a color change and we can monitor that color change on the following graph. Now, once this reaction takes place, this oxygen of the Serene and the active side is oscillated. So this entire group is attached onto the oxygen as shown and this is the Covalent bond that is temporarily formed. Remember, Chimetrypsin uses Covalent catalysis and that means we form a temporary Covalent bond.