We concentrate on atmospheric aerosol chemistry and its link to human health and climate change. We focus on the sources, formation mechanisms and climate impacts of aerosol by combing filed observations and laboratory studies, based on high-resolution mass spectrometric, optical, and hygroscopic analysis. We are particularly interested in organic aerosol in both urban and marine environments, and actively working on the development of analytical techniques for chemical characterization of organics. We also have a longstanding interest in new particle formation, particularly in the marine environments.