What's behind a pulse? The second episode dives into the world of an ice climber, a bus driver, a woman in labor, and a senior dance club to show how the human heart and the circulatory system power our physical and emotional lives, and create the pulsing rhythm of our world.

The episode is a journey through the human gut and the process of turning food into energy to keep the body going. Humans have turned eating into culture, a way to celebrate our roots, to bring us together. But food is really just one thing: Fuel. It's where you get the power to live your life. Even when you're sitting completely still, your body needs a lot of energy to stay on. But nowhere is the need for fuel more apparent than when you push yourself to the absolute limit. And the microbiome, the bacteria living in our gut, plays a great role in all this.

A look into how the body defends itself against all odds through the stories of a nature survivalist, rancher twins, a doctor who survived Ebola and a cancer therapy recipient. The Immune System, essential to our survival every second, is the most complex and least understood piece of our biology.

Astronomers make an extraordinary discovery out in deep space when they uncover a cosmic mega-structure that's one billion light-years long. Now, investigators race to decode the hidden forces that shape the most massive and mysterious structure known in the Universe.
We dive into this space great wall's fiery birth and hunt for the weird cosmic glue that holds it together to reveal how this megastructure rewrites our understanding of the universe on an epic scale.

The white hole is a region of spacetime and that cannot be entered from the outside, although energy-matter, light and information can escape from it. In this sense, it is the reverse of a black hole. Einstein predicted strange cosmic phenomena known as white holes, but scientists have yet to prove they exist.
Today, astronomers race to find the clues that can unlock the secrets of white holes. They investigate the tiny black holes that hide in the most ancient parts of the universe to finally find the smoking gun.

There is a region of space that is dangerous for reasons we don't yet understand completely. We see an increased flux of energetic particles in this area and higher-than-usual levels of radiation. It's called the South Atlantic Anomaly. Some scientists now think the long-term effects of this danger zone may be far wider reaching than anyone ever expected, and it may even have implications for the future of humanity in space and on Earth.