When arranged into nano-architected materials like metamaterials, discrete nanostructures enable novel optical phenomena, revolutionizing the manipulation and use of light. We design these materials for applications in optical sensing, photochemistry, solar energy, radiative cooling, optical computing, and quantum communication. Inspired by nature and leveraging machine learning, we customize nano-architectures for specific needs. Our advanced optical techniques enable green, on-demand fabrication and precise property measurements at single-structure and ensemble scales.