Co-packaged optics (CPO) is an emerging advanced packaging paradigm that fundamentally re-architects data center systems by moving the optical engine—the component that converts electrical signals to optical signals and vice versa—from its traditional place on the faceplate of a switchboard directly onto the same package or substrate as the application-specific integrated circuit (ASIC). This intimate integration drastically reduces the power consumption and latency associated with driving electrical signals over copper traces across the board to remote pluggable transceivers. By bringing optics closer to the processor, CPO addresses the critical bandwidth and energy efficiency bottlenecks in next-generation high-performance computing and AI clusters, where the immense data flow between switches and processors is beginning to exceed the practical limits of electrical I/O. It represents a pivotal shift towards photonics and electronics being co-designed as a single, holistic system to enable future scalability.