5 science experiments kids can do on themselves

These hands-on STEM activities will show children how the human body works.

Kids won’t need beakers and microscopes for these biology experiments—they just need themselves!

Each of these five experiments lets children discover how a human body system works. And by doing these "tests" on their own bodies, they’ll get to see and feel exactly how their own systems function. (We promise it’s safe.)

"Going through the process of physically doing something gets people more excited than just reading about it or watching someone else do it," says Evan Barnes, a biology instructor and lab coordinator at Westmont College in Santa Barbara, California. Challenge your kids to experiment on themselves with these activities—and watch them be wowed.

The Big Jump (muscular system)

What to do: Have your kid stand with his legs straight and try to jump. Then have him bend his knees and jump again. This time he’ll probably be more successful!

Whats going on: The muscular system is made of special cells called muscle fibers that contract to help your body move. "As you crouch, the muscle fibers in your thighs, hips, and glutes contract,” MacKenzie says. “When you start to jump, the muscle fibers expand, and the effect is like a spring uncoiling." That releases the energy needed for your body to jump. When your legs are straight, the muscles don’t contract and therefore don’t release as much energy.

Spinning and Sitting (nervous system)

What to do: Have your child sit in a chair blindfolded, then stand up and spin in a circle seven times. Now, without removing the blindfold, have her try to find the seat to sit down. (Make sure you do this in a safe place that’s clear of obstacles!)

What's going on: The nervous system relies on chemical and electrical signals to communicate with the brain and different parts of the body. Those signals are sent with the help of receptors that are all over your body—including hairlike structures in the inner ear. When those receptors are touched by the endolymph, a fluid inside the ear’s semicircular canals, they send a message to the brain that your body is moving. That includes when you’re spinning around—but after you stop spinning, the fluid keeps moving.

“That sends signals to the brain, brain stem, and cerebellum, and the brain interprets this movement,” says biology instructor Jamie Parker of Fordham University in New York City. “So if the liquid is moving while you’re still, your brain still thinks you’re still spinning.”

Gallon Jug Test (respiratory system)

What to do: Fill an empty gallon jug with water and dump it into a large basin. (Tip: Do this in a sink!) Refill the jug, mark the water level on the outside, and place the cap back. Turn the jug upside down into the basin. Keeping the mouth of the jug underwater, take off the cap and have your child insert a bendy straw into the jug, with the other end sticking out above the water.

Have your kid take a big, deep breath, then blow into the straw until no more air is in her lungs. When she’s blown out all she can, place the cap back on the still-underwater jug. When you remove it from the water, you'll see the water level has gone down, and the missing water replaced by air.

What's going on: Thanks to the respiratory system, our lungs breathe in oxygen that our cells need to live, then breathe out carbon dioxide as a waste product. "[The air] we’re seeing is how much air the lungs contain in any one big exhale," says Ann Haley MacKenzie, a science educator at Miami University in Ohio. So the air shows how much carbon dioxide your child has exhaled—and how much lung capacity she has to inhale more air.

Hopping Marshmallow (circulatory system)

What to do: Have your child stick a marshmallow on top of a toothpick. (A mini one is best but any will do!) With his arm palm up on a level surface, balance the marshmallow so that the toothpick sticks straight up over his wrist where he feels a pulse. You’ll see the marshmallow stick jiggle back and forth or even hop up and down. Then have your kid jog in place or do jumping jacks for 30 seconds, and repeat. The marshmallow stick will move faster!

What's going on: The circulatory system is what causes the heart to pump blood and lymph through your body’s arteries and veins. Pumping blood into an artery creates a pulse. That’s what you feel when you press your fingertips to your wrist—and why the marshmallow stick moves when it’s balanced there. And after you exercise? “The heart pumps more strongly to send more blood to the areas of the body that are moving to bring them more nutrients and oxygen,” Parker says.

Bag of Bones (skeletal system)

What to do: Grab a friend for this experiment! With a long string, Kid 1 measures the height of Kid 2, then cuts the string there. Then Kid 2 stretches her arms out to each side, and Kid 1 uses the same string to measure fingertip to fingertip. It will be almost exactly the same length!

Now fold the string in half, and measure from the bottom of the heel to the top of the femur (just under the rear end). It will be almost exactly half the distance from fingertip to fingertip. If you unfold the same string and then fold it in half twice, it will equal the distance from the elbow to the fingertip. Finally, unfold the string and refold it in thirds, and it will equal the circumference of the head!

What's going on: The skeletal system is all about the body’s bones and how the muscles support them, helping us stand and walk. So your skeleton’s limbs must be proportionate to each other. "If these proportions are uneven, it will impact your gait," MacKenzie says. If your legs are uneven, you might limp; if your arms are too long for your legs or your skull is too big for your spine, you might have trouble balancing.

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