Striking transformations in the chemical complexity of the Earth's atmosphere have led to a multitude of pathways to aerosol formation. Likewise, the search for more efficient fuels and engine designs has resulted in similar increases in the composition of combustible fuels. These changes present opportunities to the scientific community to develop a molecular-scale understanding of the available chemical pathways in both environments. The development of predictive models for atmospheric and combustion chemistry draws upon experimental data encompassing spectroscopy, dynamics, and kinetics. Recent results from our laboratory will be discussed, focusing on the (photo)chemistry of systems relevant to the atmosphere and combustion. Using laser spectroscopy and imaging methods complemented by high-level theory, we correlate fundamental laboratory observations to novel perspectives in aerosol and energy processes.