A new study has found evidence for lung toxicity of different forms of ‘cellulose nanocrystals’ (CNCs) in mice. The study suggests that physical characteristics, such as length, of the CNC relates to the type of effect it has on the lung. These nanosized crystals, made from plant-derived materials, are increasingly being used in novel applications, such as cleaning up oil spills in water and flexible electronic displays, and consumer products, which raises concerns about their potential health impacts.