When discrete nanostructures are arranged into nano-architected materials such as metamaterials, they exhibit a plethora of novel optical phenomena, enabling unprecedented manipulation and utilization of light. We focus on creating these nano-architected materials to improve optical sensing, photochemical reactions, solar energy conversion, passive radiative cooling, optical computing, and quantum communication. Drawing inspiration from nature and employing machine learning techniques, we design nano-architected materials precisely customized for targeted applications. We develop advanced optical techniques to enable green manufacturing of these nano-architectures on demand and to measure their properties at both the single-nanostructure and ensemble levels.