Your heart completely stops beating every time you cough, and you know what? You never noticed that in your life until I told you now, but want to bet that the next time you cough you'll remember that bizarre sensation? Our bodies hide absolutely absurd secrets that work all the time right under our noses without us having the slightest clue that they're happening. Get ready, because what I'm going to show you in the next few minutes will completely change the way you see your own biological machine. When the pressure in your chest suddenly rises because of a strong cough, the nervous system takes a strategic pause to protect the organ and readjust blood flow. It's a second of absolute silence in the center of your chest that happens while you try to catch your breath. But the next one is worse, because your fingers wrinkle in the water, and science has finally discovered the real reason for this. It's not just the skin absorbing liquid like an old sponge, quite the contrary, since your nervous system creates those wrinkles on purpose. It does this by transforming your fingers into veritable rain tires so you can hold wet objects without slipping for anything in the world. It's a perfect evolutionary response that your fingers perform on their own, and you thought it was just a side effect of the pool. And then there's your hair that stands on end out of nowhere, creating that strange texture on your arms that you're surely feeling right now. They do this because your body desperately tries to make you look bigger and more threatening in the face of any invisible micro-danger. It's a distant echo of our hairy ancestors who tried to scare away ferocious predators simply by inflating their fur in fright. But listen to this, because your eyes lock onto completely invisible objects every time you blink rapidly. Your brain performs an impressive mathematical calculation to ensure that the image doesn't move while your eyelid is closed. It keeps the target fixed in the void for a fraction of a second so that the world doesn't shake every time you lubricate your vision. But pay attention to what happens when you're falling asleep, because your brain invents a false freefall just to wake you up with a start. You know that violent jolt that makes your whole body jump in bed for no apparent reason? That's your alert system interpreting deep relaxation as a motor failure and triggering a false alarm to save you. But the next one will make you pay attention to your own belly, because your stomach changes size and position every time you take a deep breath. Every time the diaphragm descends to pull in air, it pushes the organs down and alters the internal geometry of your abdomen in a fascinating way. You breathe automatically all day without noticing that there's a giant mechanical accordion working inside you right now. And speaking of things you don't see, your brain creates a perfect visual illusion to cover up the blind spot in the middle of your vision. It simply invents colors, textures, and shapes out of thin air to stick to the image and hide the black hole that your eyes let through. It's such a well-executed mental magic trick that you walk through the world thinking you see everything in continuous high definition. But be prepared, because your lungs slowly change color as you age, darkening from the inside without you feeling a thing. The rosy tissue of youth gains different marks and shades over the decades simply by interacting with the planet's air. It's the entire history of your exposure to the outside world being silently painted inside your ribcage. But the next one is truly bizarre, because your brain freezes all your saliva so you don't swallow it unnecessarily while you sleep soundly. The production of liquids in your mouth decreases drastically and the consistency changes so you don't choke on your own drool during the night. It's a nocturnal safety mechanism that works in absolute silence to ensure you survive the entire night. And there's more, because your nose memorizes trillions of different smells throughout your life and stores them all ready to save you from sudden danger. A single odor molecule is capable of triggering old memories and defense reactions before you can even reason about what you're smelling in the air. Your sense of smell is an ultra-sophisticated chemical radar that never rests, not even when you're distracted by something else. But pay close attention to this, because your eyes project an exact blind spot that your brain fills in on its own with visual lies all the time. There's a region in your retina where the optic nerve connects, and there's no...