Nanoscale confinement can be defined as a space confined by interfaces with at least one nanometer-scale dimension. Objects under nanoscale confinement have a large ratio of interfacial area to volume that makes interfacial properties have significant impact. This dissertation examines three cases in which liquids are confined between solids. The main focus (two papers) describes how electrostatic interactions between two interfaces affect ions confined within the liquid. Commonly, the charge distribution near an interface is described by electrical double layer model, where the characteristic decay length of the potential is the Debye length κ^(-1), which is typically 1–100 nm. In a nanoscale confinement, the electrostatic potential from both confining surfaces overlaps, and there is no bulk solution in the confined liquid. If the two surfaces have the same potential in isolation, the potential will increase throughout the liquid phase. I examine two hypotheses for ions under confinement in aqueous solution: (1) diffusion of ions will be hindered by the electrostatic potential; (2) surfactants will form surface aggregates (a form of micelles) that would not occur without the modified potential. To test the first hypothesis, I studied diffusion of fluorescein sodium salt in the nanoscale water confined between glass surfaces. The confining glass surfaces were fabricated by thermally bonding Borofloat glass wafers. Fluorescence microscopy was used to monitor the amount of fluorescein throughout the confined water, and thereby to understand the diffusion Measurements with done for a variety of different Debye lengths and water film thicknesses. I found that the time for fluorescein to reach equilibrium distribution in the nano-scale confinement could be 10× longer when there was no salt initially present compared to when salt was present. However, even a small amount of salt initially in the confined liquid led to a very weak effect of Debye length on diffusion. Thus, provided that the surface potential inside a thin film is initially screened by even a low concentration of electrolyte inside the confinement, diffusion is unhindered. A practical application of this result is delivery of dissolved species should not be preceded by infusion of pure water into pores if speedy delivery is desired. For the second hypothesis, I studied adsorption and aggregation of dodecyltrimethylammonium bromide (DTAB), a cationic surfactant, within the same type of nanoscale confinement by Borofloat glass. A fluorescent dye, Nile red, whose fluorescence depends on its solvent environment was used to indicate formation of surface aggregates by the surfactant. We found that surface aggregation of DTAB occurred at a very low surfactant concentration (