A single wood cell wall is constructed from fibers of cellulose - nature's most abundant polymer. Within each fiber are reinforcing cellulose nanocrystals (CNCs), which are chains of organic polymers arranged in nearly perfect crystal patterns. At the nanoscale, CNCs are stronger and stiffer than Kevlar. If the crystals could be worked into materials in significant fractions, CNCs could be a route to stronger, more sustainable, naturally derived plastics.