The Prather group conducts research focused on improving our understanding of how humans are influencing our atmosphere and climate. In the early part of her career, Prof. Prather and her research group developed a unique method, aerosol time-of-flight mass spectrometry (ATOFMS), for the on-line characterization of the size and chemical composition of atmospheric aerosols. Using ATOFMS and a wide array of other gas and particle instruments, the Prather group is now performing studies worldwide to better understand the role of aerosols in climate change. The ultimate goal of the group's research is to determine which aerosol sources play the largest role in affecting key atmospheric processes, including heterogeneous reactions, cloud formation, and ice nucleation. The Prather group is aiming to understand the full cycling of atmospheric species as depicted in the figure below. All of these processes are ultimately affected by the chemical composition of individual particles. Traditional chemical analysis methods measure the average composition of an ensemble of particles and thus cannot be used to predict or explain the behavior of individual aerosol particles, as individual aerosol particles have a variety of compositions.