Since the beginning of the 21st century the nanotechnologies have grown enormously, judging simply by the number of products now on the market and the funds dedicated to research and development. In 2014 there may be as many as ten million people--about 11% of the total manufacturing sector's workforce--employed in processes using nanotechnologies. Although the whole scientific community has now put its back into narrowing the gaps in scientific knowledge, and promoting research with a view to tackling the potential risks of nanotechnologies, we are still far from any firm agreement. In order to respond to these needs the research in occupational medicine will have to focus on the key questions that are still open, especially those on risk assessment to safeguard the health of the increasing numbers of workers who will be employed in these various sectors. These questions centre on toxicity and health effects, extent of translocation to target organs and importance of dermal exposure.