The clouds over your head may have started around a seed made of a seashell. Microscopic algae called phytoplankton can affect the amount of clouds that form and even how they move.

One such species, Emiliana huxleyi – known as Ehux – is a single cell encased in overlapping lacy discs of calcium carbonate. When Ehux is infected with a virus known as EhV, the cell sheds its chalky exoskeleton. Sea spray can fling these frisbee-shaped scales into the air, where they can become the …