The release of pollen from vegetation represents a major seasonal, pulsed source of organic matter to the atmosphere of great biological and societal importance. While pollen grains themselves are relatively large (20-100 microns) and do not contribute to fine particulate matter, the rupture of pollen grains under moist conditions can lead to hygroscopic, fine particulate matter that may be climatically relevant. The proposed work will use metabolomics on whole grain pollen and atmospheric aerosol samples to qualitatively explore the organic signatures in atmospheric aerosols. Specifically, we will use ultra high-resolution mass spectrometer ion cyclotron resonance (ICR) and liquid chromatography coupled to Orbitrap (LC-MS) at EMSL to analyze the whole grain and ambient aerosol samples to characterize the chemical and metabolic composition of aerosols and pollen. Supplemental analysis using electron scanning microscopy and ice nucleation experiments will further improve our insight into the role of pollen in the atmospheres. These findings will improve our understanding of biological aerosols in the Earth system and their contribution to cloud formation in the atmosphere.