Cell interfacing, which includes the stimulating and recording of cellular activities, is a fundamental theme in modern biological research. Traditional cell interfacing methods have predominantly relied on transducing biochemical signals from biological components into electrical signals and vice versa, confined largely to the electrical domain. To complement these strategies, the advent of fluorescent protein-based sensors and optogenetics has expanded cell interfacing modalities into the optical domain, offering unparalleled specificity and precision. This thesis delves into the development of scalable, high-density optoelectronic arrays designed for high-precision cell interfacing. Through the engineering of four distinct devices capable of either stimulating or recording cellular activities—or achieving both—with a focus on single-cell level spatial resolution, this work promises to enhance our capacity to unravel the coordination of complex biological systems and the underlying mechanisms of biological processes. First device introduced is a high-yield, silicon-based passive photodiode array designed for the optical recording of cellular signals. We examined the optoelectronic performance of the array, highlighting its low light intensity detection limit and rapid scanning capabilities, showing its promise as an on-chip fluorescent imager for optical monitoring of cellular signals. Second device presented a high-density, blue micro-LED array that enables single-cell manipulation of calcium dynamics in human embryonic kidney (HEK) cells. Based on the micro-LED work, the third device explores the development of dual-color micro-LED arrays for bidirectional optogenetics through a novel quantum dot patterning strategy combined with the coating of spectral filter layers. Lastly, the fourth device presented a silicon shank integrating dual-color micro-LEDs and microelectrodes for in vivo bidirectional optogenetic electrophysiology. This device enables the excitation or inhibition of neuronal activities in the mouse cortical regions with layer specificity. Collectively, this thesis presents four distinct cell-interfacing devices that combine scalability with high precision, offering an optical complement to traditional electrical interfacing methods. By applying these devices both in vitro and in vivo, we demonstrate a novel approach to interrogating cellular dynamics, which has profound implications for decoding neural circuits and mapping cellular networks at the cellular level.