This review discusses recent advances concerning morphologies and functions obtained from single-chain nanoparticles (SCNPs). SCNPs are unimolecular, soft nano-objects consisting of individual polymer chains collapsed to a certain degree by means of intramolecular bonding. Many of potential applications of SCNPs rely on their peculiar molecular morphology adopted in solution. SCNPs coming from random or block copolymers can yield ordered structures by self-assembly in a wide range of morphologies including spheres, cylinders, bicontinuous structures, lamellae, vesicles, and many other complex or hierarchical assemblies. These nanocomposites can provide practical applications, still in their infancy, in several fields. The classification of SCNPs according to their morphologies will help to link their function to the specific applications.