The impact of aerosol particles from anthropogenic and natural sources on clouds is a large source of uncertainty in our ability to predict the present climate. It is a multifaceted problem that necessitates laboratory studies, observations in the ambient atmosphere and model simulations from the molecular scale to the global scale. This workshop will bring together new avenues of work by scientists in this field with complementary backgrounds. One group (led by Cziczo and Bertram) will focus on phase transitions that are fundamental to how aerosol particles nucleate water droplets and ice crystals in clouds. The second group (led by Riemer and Leaitch) will focus on how clouds are impacted by changes in aerosol particles based on field observations, satellite observations and modeling studies. The schedule will be coordinated to allow for exploring connections amongst all participants.