A Self-Contained Biogeochemical Reactor (IMAGE) Max-Planck-Gesellschaft Caption The Amazon ecosystem produces organic aerosol particles, which serve as the condensation nuclei for water vapor. They therefore trigger the formation of clouds and precipitation, driving the hydrological cycle. Credit Image: MPI for Chemistry Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.