Life & body
Life & body
Seeds, hearts, senses, and growing things
A defence aimed at nothing
Why Does Pollen Make Some People Sneeze?
An allergy is your immune system mounting a real defence against something harmless, and the symptoms are the defence, not the pollen.
Let’s go →A planned demolition
Why Do Leaves Change Colour?
Trees break down their green pigment and cut leaves loose before winter, revealing the colours underneath.
Let’s go →A windscreen wiper you never think about
Why Do You Blink?
Blinking spreads a fresh layer of tears across your eye, and your brain edits out the moment of darkness.
Let’s go →Four things in a river
What Is Blood Made Of?
Blood is mostly water, carrying red cells, white cells and platelets around the body.
Let’s go →The one blush you cannot fake
Why Do You Go Red When You Are Embarrassed?
Blushing is blood vessels in your face opening on their own — a signal you cannot start, stop, or fake.
Let’s go →Stiff and springy together
What Are Bones Made Of?
Bone mixes hard mineral with flexible protein, giving strength without brittleness.
Let’s go →Predicting, not just reacting
What Does Your Brain Do?
The brain constantly predicts what is happening and corrects itself using the senses.
Let’s go →Fetching oxygen, dumping waste
Why Do We Breathe?
We breathe to collect oxygen for burning food and to get rid of carbon dioxide.
Let’s go →Watching blood being cleared up
Why Does a Bruise Change Colour?
A bruise changes colour because the spilled blood is dismantled in stages, and each stage is a different colour.
Let’s go →Air that took a wrong turn
Where Does a Burp Come From?
A burp is swallowed air coming back up — gas rises through liquid and the top of your stomach is the only way out.
Let’s go →The colour it refuses
Why Are Leaves Green?
Leaves are green because chlorophyll absorbs red and blue and reflects green.
Let’s go →A sudden gale, from inside
Why Do You Cough?
A cough seals your airway, builds pressure behind it, and releases it as a blast fast enough to sweep the tube clear.
Let’s go →Being eaten by the invisible
Why Do Dead Things Rot?
Rotting is microbes eating dead matter and returning its nutrients to the soil.
Let’s go →Fluid that keeps going
Why Does Spinning Make You Dizzy?
Dizziness happens because the fluid in your ear keeps swirling after you stop, so your ears insist you are still turning.
Let’s go →A brain rehearsing offline
Why Do We Dream?
Dreams happen while a sleeping brain replays and sorts the day, with the body held still.
Let’s go →Demand outrunning supply
Why Does Exercise Make You Puff?
You puff during exercise because muscles need far more oxygen than at rest.
Let’s go →A backstop for your fingertip
What Are Fingernails For?
Fingernails are a hard backstop that lets your soft fingertip press against something, making fine touch and picking things up possible.
Let’s go →Energy passed along
Who Eats Whom?
A food chain follows energy from sunlight through plants and animals.
Let’s go →Living things too small to see
What Are Germs?
Germs are microscopic organisms that multiply in your body and cause illness.
Let’s go →Moving the focus point
How Do Glasses Help You See?
Glasses pre-bend light so the image lands exactly on the back of your eye.
Let’s go →A reflex for fur you lost
Why Do You Get Goosebumps?
Goosebumps are tiny muscles pulling your hairs upright, a leftover reflex from furry ancestors.
Let’s go →Cartilage turning into bone
How Do You Grow Taller?
You grow taller at soft zones near the ends of your bones, mostly during sleep.
Let’s go →A name that is probably wrong
Do Growing Pains Really Come From Growing?
Growing pains are real aches with a misleading name — bones grow far too slowly and too painlessly to be the cause.
Let’s go →Dead rope, pushed out of a living hole
Why Does Cutting Hair Not Hurt?
Cutting hair does not hurt because the living part is buried in your skin and the visible strand is dead protein.
Let’s go →Vibration turned into signals
How Do You Hear?
Hearing converts air vibrations into nerve signals through the eardrum and hair cells.
Let’s go →A pump squeezing
What Is a Heartbeat?
A heartbeat is a muscle squeezing blood around your body's loop.
Let’s go →An empty tube, squeezing anyway
Why Does Your Stomach Rumble?
A rumble is your empty stomach and gut sweeping themselves clean, and hunger is a hormone clock, not an empty feeling.
Let’s go →Guess everything, keep what works
How Does Your Body Fight a New Germ?
Your immune system makes millions of random shapes in advance, then mass-produces whichever one happens to fit the invader.
Let’s go →A recipe, copied twice
Why Do You Look Like Your Parents?
You inherit half your instructions from each parent, shuffled into a brand new combination.
Let’s go →Seven metres of grabbing
Why Are Your Intestines So Long?
Your intestines are long because food is only absorbed at the wall, and length, folds and fuzz all buy more wall.
Let’s go →Drowning out one signal with another
Why Does Scratching Feel So Good?
Itch travels on its own slow nerves, and scratching drowns it out with pain signals your spinal cord prioritises.
Let’s go →Throw it all out, take back what you need
What Do Kidneys Actually Do?
Kidneys clean blood by throwing nearly everything out and carefully taking back the water and salt you need.
Let’s go →The chemistry room
What Is a Liver For?
The liver is where everything you absorb goes first — to be stored, rebuilt into something useful, or made safe.
Let’s go →Half a tennis court, folded up
Why Are Lungs Spongy Instead of Hollow?
Lungs are spongy because oxygen can only cross where air touches blood, and folding gives an enormous amount of touching.
Let’s go →Only ever pulling
How Do Muscles Move You?
Muscles move you by pulling, which is why they come in opposing pairs.
Let’s go →The tip of something bigger
What Is a Mushroom?
A mushroom is the spore-making fruit of a much larger underground fungus network.
Let’s go →An alarm, not a measurement
Why Does It Hurt?
Pain is an alarm your brain chooses to sound — which is why the same injury can hurt very differently.
Let’s go →Building food from air
How Do Plants Eat Light?
Plants use sunlight to build sugar out of air and water.
Let’s go →Pollen reaching the right place
What Is Pollination?
Pollination is pollen moving between flowers so that seeds can be made.
Let’s go →Anchor and straw
What Do Roots Do?
Roots anchor a plant, absorb water and minerals, and trade with soil fungi.
Let’s go →A net, cast in seconds
How Does a Cut Stop Bleeding?
A cut stops bleeding when platelets plug the hole and a protein mesh forms across it, trapping blood cells into a scab.
Let’s go →A plant and its lunch
What Is Inside a Seed?
A seed contains a tiny plant and a food store to launch it.
Let’s go →Muscles working for the heat, not the movement
Why Do You Shiver When You Are Cold?
Shivering makes your muscles do pointless work on purpose, because most of what a muscle produces is heat.
Let’s go →Light in, picture built
How Do Your Eyes See?
Eyes convert light into nerve signals, and the brain builds the image.
Let’s go →More than a wrapper
What Does Your Skin Do?
Skin keeps things out, controls temperature, senses the world and repairs itself.
Let’s go →Maintenance time
Why Do We Sleep?
Sleep is when your body repairs and your brain sorts and stores the day.
Let’s go →Catching actual molecules
How Does Smelling Work?
You smell things because their molecules float into your nose and lock onto receptors.
Let’s go →Blasting the nose clear
Why Do We Sneeze?
A sneeze is an automatic blast of air that clears irritants from your nose.
Let’s go →Taken apart, then absorbed
What Happens to Food You Eat?
Digestion breaks food into molecules small enough to enter your bloodstream.
Let’s go →Cooling by evaporation
Why Do We Sweat?
Sweating cools you because evaporating water takes heat from your skin.
Let’s go →Five basics, plus your nose
How Does Taste Work?
The tongue detects five basic tastes; the rest of flavour is smell.
Let’s go →Three kinds of tear
Why Do We Cry?
There are three kinds of tears: constant maintenance, emergency rinsing, and emotional ones.
Let’s go →A toolkit in your mouth
Why Do Teeth Have Different Shapes?
Teeth have different shapes because cutting, tearing and grinding need different tools.
Let’s go →A saltiness detector
How Does Your Body Know You Need a Drink?
Thirst comes from a patch of brain measuring how salty your blood is, not from a dry mouth.
Let’s go →Several senses at once
How Does Touch Work?
Touch is several different senses working together in your skin.
Let’s go →Some of it — and the sea makes more
Do Trees Make the Air We Breathe?
Trees make oxygen, but tiny ocean plankton produce about half of it.
Let’s go →A rehearsal
How Do Vaccines Work?
Vaccines train your immune system on a harmless preview of a germ.
Let’s go →Two flaps, flapping very fast
How Do You Make Your Voice?
Air from your lungs makes two flaps in your throat vibrate, and your mouth shapes that buzz into speech.
Let’s go →A bag that reports on itself
Why Can't You Just Hold It Forever?
Your bladder measures stretch, not volume — which is why the urge comes in waves and why cold makes it worse.
Let’s go →