The arrangement of cellulose microfibrils in the cell wall from different tissues of wheat straw was investigated mainly using atomic force microscope (AFM). It was revealed that cellulose microfibrillar crystals arrange randomly in the parenchyma cell walls and are ordered quite well longitudinal to the fiber axis in the epidermal fibers. The microfibrillar crystals are about 20 nm in diameter and 150-200 nm in length. Moreover, the cellulose microfibrillar crystals in the epidermal fibers align periodically along the fiber axis and the periodicity is similar to the length of the fibrillar crystals. This structure was confirmed by small angle X-ray scattering (SAXS). (c) 2007 Elsevier Ltd. All rights reserved.