Atomic force microscopy (AFM) was used to image the microfibrilar network of celery parenchyma cell wall material (CWM), before and after each step in the selective extraction of pectins and hemicelluloses. The images collected were subjected to image analysis and the diameters of the cellulose microfibrils were measured following each step in the extraction process. Not only was an increase in the mean size of the microfibrils observed as the pectins were selectively removed, but an increase in the proportion of large to small microfibrils was also observed. This suggests that removal of the pectic matrix not only results in the swelling of existing microfibrils, but also removal of pectins would enable the microfibrils to move closer together within the cell wall, and hence have a greater tendency to self-associate and form aggregates. (C) 2009 Elsevier Inc. All rights reserved.