Over the last decade, the structural refinement of cellulose allomorphs and their analogs has been advanced using high-resolution fiber diffraction. This also includes structures of crystals complexed with small molecules, which can inherently involve disorders. Computational methods, including density functional theory, in combination with molecular modeling are leading to improved structural analyses. Spectroscopic techniques such as vibrational spectroscopy give quantitative and robust data directly related to structural insights on cellulose. These data will benefit from improved molecular modeling's capacity for interpretation and will also serve as a gauge to measure the capacity of molecular modeling as an aid in structural determinations. Improvement in the capacity to directly simulate experimental data such as that from scattering, diffraction, and spectra will be the key for further integration of modeling and experimental approaches.