Plot: Have you ever thought that when we breathe a little bit of heaven enters each of us? But what exactly is the sky? Is it possible to be struck by lightning out of the blue? What exactly is a rainbow made of? We discover all this with a journey into the 100 kilometers of air above our heads; this is by definition the sky. In the episode we try to explain what a cloud is and why the sky is blue during the day and then suddenly becomes transparent at night and allows us to see the stars that cannot be seen during the day