This paper reviews the framework that underpins the development of a new generation of personal samplers capable of operating at much lower flowrates that those of the current generation and so capable of being used for exposure assessment not only for 'traditional' occupational populations (i.e., industrial workers) but also for people exposed to aerosols in the ambient atmosphere (including children). The opportunity for this new generation of samplers stems from the availability of very light and compact low-flowrate pumps. The development and deployment of such instruments presents: (a) physical challenges in terms of how to collect particle size fractions in a manner which is consistent with the new particle size-selective sampling criteria, and (b) analytical challenges in terms of how to quantitate the much smaller amounts of collected material that need to be analysed. The paper lays out the physical and analytical scenarios, and points the way forward to how such challenges can be overcome. Work is already in progress in several countries to develop prototype instruments for applications like those described.