Bioelectricity regulates vital signaling and regulatory processes across all levels of biological organization—from transient ion channel activity in single cells to the coordinated electrical rhythms of tissues and organs. Achieving dynamic and precise spatiotemporal control over these bioelectrical events is essential for both fundamental biological understanding and therapeutic intervention. However, existing electrophysiological and neuromodulatory interfaces often lack the resolution, adaptability, and biocompatibility required for seamless integration with complex, living systems. This thesis presents the development of multiscale spatiotemporal optoelectronic biointerfaces, which integrate innovations in materials design, device engineering, and biophysical modulation to enable high-fidelity and minimally invasive control of bioelectricity. At the core of this work are two novel material systems designed for targeted photoelectrical modulation: monolithic nanoporous silicon, which facilitates high-density, spatiotemporally confined photocurrent injection for neuronal and cardiac applications; and self-organized gold–titania plasmonic metasurfaces, which enable spatially tunable photocarrier dynamics, offering new modalities for localized stimulation and sensing. Building on these material platforms, the thesis introduces a class of heterospatial optoelectronic supercapacitor devices, which integrate photoresponsive and capacitive elements into ultrathin, flexible, and implantable architectures. These devices support low-intensity, in-depth photostimulation without the need for genetic modification and are validated in vivo for both peripheral nerve activation and cardiac modulation, including the successful optical pacing of large-animal hearts. To complement these stimulation platforms, a tissue-like, stretchable mesh bioelectronic system is developed for continuous monitoring, diagnostics, and therapeutic intervention. Engineered to match the mechanical properties of biological tissues, these mesh interfaces ensure stable, long-term coupling with dynamic organs such as skin, muscle, and internal soft tissue. This body of work establishes a comprehensive framework for light-mediated control and interrogation of bioelectric phenomena across spatial and temporal scales. It lays the groundwork for a new generation of adaptive, minimally invasive, and multifunctional bioelectronic implants, advancing both our understanding of physiological bioelectricity and the development of clinically translatable photoelectroceutical technologies.