This Faraday Discussion will focus on the rapidly evolving field of nanoparticle (NP) self- and driven assembly, with a view to understanding how evolving developments in the fundamentals can be translated into science/property principles underpinning applications. There is a need for the study of disordered self-assemblies of nanoparticles, in contrast with the focus in the literature which has been on ordered nanoparticle assemblies. This contrast is similar to that between the amorphous structures assumed by many classes of polymers vs. the ordered crystalline state that is the ground state of many atomic systems. Over a century of work shows that both of these structural motifs have significant, complementary and different consequences on applications. Exploring this disordered class of NP assemblies will be a central focus. While there has been considerable interest in quiescent assembly, the more important scenario for applications is external-field driven assembly, as may be found when these materials are processed. This meeting will cover three distinct classes of materials where nanoparticle assembly holds significant potential for applications, with a view to determining common features of structural organisation on the nanoscale. The meeting will also be an opportunity to consider the implications of these ideas for the broader field of soft matter.