Abstract: A method of separating carbon nanotubes having substantially the same diameter including the steps of: providing a sample of carbon nanotubes; separating individual nanotubes within the sample, and mixing with a solution comprising fibrous protein fibrils so that at least some individual nanotubes form a complex with the protein fibrils, and separating out those nanotubules which have formed a complex. Preferably the protein is collagen. The separated nanotubes can be used in the fields of electronics, medical and materials science.