Light-matter interactions are central to a wide range of scientific and technological disciplines. Though optical interactions have been important to advancing our understanding of atoms, molecules, and materials, the microscopic details of how light manipulates matter are often poorly understood. A material's optical response is complex, determined by coupled manybody interactions that vary on an atomic length scale. While data is needed to combat this complexity, it has generally not been possible to probe the microscopic details of light-matter interactions.

We have recently demonstrated a novel x-ray scattering technique, x-ray and optical wave mixing, that directly probes the atomic scale details of how light manipulates electronic charge in a material. I will discuss how this x-ray scattering method provides information on the atomic scale optical response of a material and offer a few speculations on how this might help us better understand, and ultimately control, materials.