Atmospheric aerosols are tiny particles that scatter and absorb sunlight but also influence climate indirectly through their role in cloud formation. One of the largest sources of aerosols is sea spray which is produced over the world’s oceans. Understanding how these particles take up water from the atmosphere, their so-called hygroscopicity, is important because it determines how much sunlight they reflect and how well they can form clouds. This was the topic of a new study by researchers from Stockholm University and international partners published in Nature Communications.