Molecules that have different molecular packing arrangements despite identical chemical composition are said to be polymorphic. The variety of possible forms, each an allomorph (or polymorph), presents opportunities and challenges in various fields – including the drug industry and agriculture and forestry. In this blog, we talk to United States Department of Agriculture (USDA) Research Scientist Emeritus1 and the Editor-in-Chief of Cellulose, Dr Alfred D. French about his work with cellulose, which has multiple polymorphs (allomorphs).