Aerosols are tiny particles in the air, and some of them help form cloud droplets (called cloud  condensation nuclei). Most ship measurements focus on only one ocean. To compare aerosols  over several oceans, we measured them during a transit voyage of a research ship using the  same method. The results show that properties of these particles cannot be represented by a  single marine condition. Moreover, they changed widely, depending on where the air came  from and the pathway it traveled.