Bacteria, viruses, but also fungus spores, algae, pollen, and even insects: microorganisms are constantly drifting through the sky. How can so many living beings find their way into the air and be circulating in our atmosphere? How do they survive? What is their influence on our lives and our entire living world? Biodiversity, health, climate - scientists are only now discovering just how much this discreet airborne "plankton" affects our lives and the entire ecosystem on Earth. But despite its many virtues, this magic matter is now under threat from human activity. With help from experts and using 3D visual effects, this scientific investigation will take us to the heart of a world that is still very little understood, and will reveal the diversity and fragility of the air we breathe.