<p>This study follows the generation of microfibrils from kraft pulp, by fractioning ten samples extracted from commercial mechanically produced cellulose nanofibrils (mech-CNFs). SEM and AFM imaging revealed that during mechanical treatment, the outer cell wall (P and S₁) and/or possible parts of S₂-layer, detaches from the fibre structure as ribbons and flakes, but can also remain partially attached with the fibre core. Further processing induces internal fibrillation in the flakes and ribbons, resulting in the delamination and formation of microfibrils. These microfibrils can still be attached to the fibre structure. Interesting properties were shown for what would be considered very coarse fibres. This improves knowledge on mech-CNF production and provides further understanding of mech-CNF interactions in different applications.</p>