Summer at the North Pole: In August and September 2018, the Swedish research vessel Oden was made fast to a large ice floe. Forty scientists conducted a variety of research projects on the ice and on board. In the "Swiss container", self-evidently red with a white cross, PSI researchers Julia Schmale and Andrea Baccarini studied the aerosols of the Arctic. These naturally airborne suspended particles are produced by, among other sources, microorganisms that live in the water and ice. The ascending aerosols lead to the formation of clouds and in doing so play a crucial role in Earth's climate. Thus this research project helps to improve understanding of human-made climate change.