This study provides insight into hydration of two significant atmospheric compounds, glyoxal and methylglyoxal. Using synchrotron radiation excited X-ray absorption spectroscopy, we confirm that glyoxal is fully hydrated in water, and for the first time, we experimentally detect enol structures in aqueous methylglyoxal. Our results support the contribution of these compounds to secondary organic aerosol formation, known to have a large uncertainty in atmospheric models and climate predictions.