We investigate and experimentally control the light-matter interaction at the nanoscale by leveraging advancements in photonics and quantum optics. Our main objective is to conceive new optical measurement tools and experiments with ever-increasing sensitivity and resolution to address problems in chemistry, materials science, and quantum science. Many condensed-phase nano-materials exhibit considerable structural complexity and rich multi-timescale dynamics that can both be measured and increasingly tuned with light. Each material system poses a different set of questions, yet we believe the answers can be found with our experimental approaches rooted in spectroscopy, nanophotonics, and quantum optics.