Engineered nanoparticles have been recognized as promising tools for targeted delivery of pharmaceuticals or genes to particular cells.In recent years, however, concerns have been voiced that nanoparticles could be hazardous to human health.To fully exploit the benefits of nanobio-technology while avoiding potential health hazards, we aim for an in-depth understanding of the interactions between nanoparticles and biomatter at the molecular level.To this end, nanoparticle modification, processing and degradation upon contact with cells, tissues and organisms need to be studied, and biological responses to nanoparticle exposure have to be thoroughly assessed.