Abstract
Within 5 years of its first publication in December 2004, Particle and Fibre Toxicology has become a well recognized open access, peer-reviewed, online journal with an (unofficial) impact factor of 5.5. This major achievement is due to the dedication of former Editors-in-Chief Professors Ken Donaldson and Paul Borm, and, of course also due to the high quality of manuscripts that have been submitted by authors from all over the world. Recent years have shown a significant increase in papers dealing with nanomaterials and nanotoxicology, whilst the small margin between ambient PM exposure and current standards continues to provide a constant flow of manuscripts on this topic. This however, does not imply that we can relax now.