MS is routinely used to selectively detect the amount of a given substance/analyte and determine the chemical composition of that analyte. The production and detection of fragments-groups of atoms or smaller portions of the analyte-provide insight into the structure of the analyte via MS. Owing to the availability of different ionization and analysis schemes, MS can be applied to the qualitative and quantitative examination of both ensembles of particles and individual clusters. In this review, we use the acronym MS to refer to both the technique and the instrument. In MS, the measurable quantity is the mas-to-charge ratio (m/z) of an collection of ions, and when the charge is unity the m/z corresponds to the ion's mass. Thus, the analyte not only has to be an innate ion or ionized in order to be detectable by MS, the m/z that an ion is detected as decreases as the charge of the ion increases. For example, the largest analytes detected by MS include biomolecules and long-chain polymers that typically have masses between several hundred kDa and a few MDa, with the former often, being multiply charged, detected at lower m/z values. A hypothetical spherical cluster of mass ≈300 Da (≈1 nm in diameter) that grows into a climatically relevant size (≈10 nm) will obtain a mass of ≈3 MDa. If singly charged, the m/z of this particle will be close the detection limit of common MS analyzers, thereby requiring the development of new instrumentation capable of detecting such a particle. In the next sections, we will provide an overview of ionization and mass analysis techniques routinely applied to atmospheric nanoparticles, discuss extensions of these techniques to gain information beyond simply mass and relative abundance, and highlight new insights gained with these techniques, primarily in the context of NPF. We will then sketch paths towards more detailed studies of small particles as well as extensions of mass analyzers to larger particles.