Developing cheaper and more efficient devices to harvest energy from the sun is a major scientific challenge. One way to increase the efficiency of solar cells ­– and even make solar cells out of otherwise inactive materials – is by covering them with a thin layer of dye that strongly absorbs sunlight and converts it into electrical current. This lecture describes our efforts to understand the basic chemical processes that take place within a dye molecule when it absorbs a photon, or particle of light. These reactions take place on very fast timescales, down to millionths of a billionth of a second, or femtoseconds. But we are able to follow this rapid, complex handoff of energy from one atom to another with SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS). The ultimate goal of this research is to design dyes that help generate electrical power with high efficiency, thus allowing us to make the most of solar energy.