The Journal of Nanoparticle Research aims to disseminate knowledge about the physical, chemical, and biological phenomena and processes associated with structures that have at least one dimension ranging from molecules to approximately 100 nanometers (or, in some cases, submicron). Novel nanoparticle research is a key component of nanoscience, nanoengineering, and nanotechnology. This journal focuses on specific concepts, properties, phenomena, and processes related to particles, tubes, layers, and macromolecules, as well as finite structures in the nanoscale range, including clusters. We consider the synthesis, assembly, transport, reactivity, and stability of such structures. The development of in situ and ex situ instruments for characterizing nanoparticles and their interfaces should be based on new principles for detecting properties and phenomena that are not yet well understood at the nanoscale. Modeling and simulation may include atomic-based quantum mechanics, molecular dynamics, single-particle, many-body, and continuum models, fractals, and other methods suitable for simulating particle synthesis, assembly, and interaction processes. We emphasize the realization and application of systems, structures, and devices with new functionalities obtained from precursor nanoparticles. Methods may include processes based on gases, liquids, solids, and vacuum, size reduction, and chemical and biological self-assembly. We encourage collaborative approaches from different disciplines and technologies, as well as interactions between researchers and users in this field.