This chapter offers a comprehensive overview of methods and concepts used to study and interpret polymer behavior at the nanoscale. It starts with an introduction to nanoscale surface morphology, highlighting how structural and topographical features influence the physical, mechanical, and chemical properties of polymers. Advanced imaging techniques such as Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) are covered for examining nanoscale structures, surface roughness, and wettability. X-ray–based methods like Small-Angle X-ray Scattering (SAXS), Wide-Angle X-ray Scattering (WAXS), and X-ray Diffraction (XRD) are also included for their ability to reveal crystallinity, molecular orientation, and nanoscale organization. The impact of processing parameters and additives on polymer morphology is discussed, with special focus on blends, copolymers, and phase separation in block copolymers. Interfacial aspects such as polymer–substrate interactions, polymer–polymer boundaries, and interfiber contacts in nanofibers are analyzed to explain their roles in adhesion, stability, and molecular packing. Additional tools like X-ray Photoelectron Spectroscopy (XPS) and Dynamic Light Scattering (DLS) are highlighted for investigating chemical composition and nanoscale particle size distributions. By integrating these techniques and perspectives, this chapter establishes a comprehensive framework for linking nanoscale structure and interfacial properties to the overall behavior of polymer systems.