It has been also found that different cellulose sources are composed of different and very small crystallite sizes [287]. Thus, this crystallite size has presented a strong relationship with the pattern recorded by the diffraction experiment. This size has been defined firstly by Scherrer [288], who found a relationship between the crystallit size and the width of a given peak at half its maximum (pwhm), represented in the following equation:τ 5 Kλ βcosθ (5.1) where τ is the size perpendicular to the lattice plane represented by the peak in question, K is a constant that depends on the crystal shape, λ is the wavelength of theincident beam in the diffraction experiment, β is the pwhm in radians, and θ is the position of the peak (half of the plotted 2-θ value).