Nanoscale devices traditionally rely on external, macroscopic voltage sources to establish their electrostatic potentials and fields ( e.g., batteries, fuel cells, power supplies). This study explores a general method by which potentials and fields can be established in situ using solid-state effects inherent in devices themselves. Endogenous electrostatic potentials (EEP) and endogenous electric fields (EEF) are created via physical junctions between metals or semiconductors having dissimilar chemical potentials for their mobile charge carriers. When expressed at the boundaries of materials, especially across narrow gaps, these EEPs and EEFs could have broad utility in nanotechnology. The magnitudes of EEPs are limited to about 4.5V; however, at the nanoscale EEFs can be as intense as any achievable using external biasing, while obviating the need for external voltage sources and electrical leads. Endogenous potentials and fields can be sustained indefinitely without power consumption and can regenerate quickly at system boundaries. In this paper the theory of EEPs and EEFs is introduced in the context of several potential nanotechnological applications, including charged particle optics and chemical catalysis; sorting and filtering of dielectric nanoparticles; spectroscopy of dipolar molecules; and the actuation of NEMS and MEMS.