Look up at the sky.

It appears empty.

But the atmosphere is filled with life.

Microscopic organisms can travel through the air, drift across continents, survive extreme conditions, and become part of ecosystems far from where they began.

The sky is not empty.

It is a highway.

And much of the life traveling through it is almost completely invisible to us.

In The Sky Is Full of Invisible Life, we explore the hidden world of airborne microorganisms and the remarkable biological processes taking place high above Earth's surface.

And extreme dryness can make the atmosphere a difficult place for living organisms.

Yet many microorganisms have remarkable survival strategies.

Some can remain dormant.

Others form resistant structures.

And some can potentially remain vi ...