We have studied mixed FA water clusters using photoionization mass spectrometry cou- Our theoretical results on photoionization dynamics in the formic acid water system will guide future experiments using ultrafast pump-probe spectroscopy being developed within our groups. We seek to measure the direct dynamics that occur between formic acid and water as the number of each moiety increases in the system. The interplay between FA and water particularly in the microscopic regime has also crucial bearings at the air-ice 5 and airwater interfaces, and in catalytic chemistry. We believe that these results will contribute to a better understanding of nucleation, cloud formation and chemistry that occurs on aqueous interfaces and aerosols by providing a molecular-level detail of how formic acid and water interact to form very stable clusters.