Human: The World Within takes a deep dive into the universe that's inside each and every one of us by exploring a shared biology that we often don't take the time to appreciate or understand. Heart, brain, eyes, blood, tears: Human uncovers not only the science behind how our bodies work, but how what's inside powers every moment of what we do out in the world. Personal profiles of people from around the globe become entry points into deeper stories about how the body's many systems function. The series takes six systems and charts a journey through their inner workings: the nervous system, the circulatory system, the digestive system, the immune system, the sensory system, and the reproductive system. Experts at the cutting edge of science and medicine reveal how the amazing feats humans can perform trace back to the incredible resilience of the human body. Radiolab's Jad Abumrad narrates the journey through this universe within and reveals what makes us tick.

Episode 1: React How do you react to the world around you? Through the lens of a boxer, a first responder, a cell tower climber and a man with a bionic limb, we'll go deep into the universe of the most powerful machine on earth: the human brain and the vast nervous system it controls. Episode 2: Pulse What's behind a pulse? This 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. Episode 3: Fuel Running through the middle of our bodies, the human gut processes the fuel our bodies need to keep going. It's also home to an entire ecosystem whose power we're just beginning to uncover. Through the worlds of a religious faster, an ultra-marathon runner, a young girl beating allergies, and a farmer we go deep into this world within. Episode 4: Defend Every minute of every day, our bodies are fending off microscopic threats with extreme precision and speed. This episode looks at a nature survivalist, rancher twins, a doctor who survived Ebola, and the recipient of a cutting-edge cancer therapy to uncover the wildly advanced biology that keeps us alive against all odds. Episode 5: Sense How do the five senses really work? In fact, there are many more than five, and they all work together to create our own version of reality. We dive into the stories of a pairs figure skating team, a perfumer, a cave explorer, and a musician to decipher how different ways of sensing the world all create their own vivid, and unique, picture. Episode 6: Birth Every single person on this earth has at least one thing in common: they were born. This episode goes on a journey with parents who are preparing for new life to see how our bodies create and sustain new life. Through their stories we learn about what is fundamentally shared and absolutely unique about the experience of birth.