Think about your lunch, the food you ate today. The part of it that your body cannot use is poop. The waste and extra water that your body does not need become pee. Each one takes its own path out of your body, and both paths start with the food and drink that you take in.

Food goes in at your mouth, and that is where the trip begins. It travels through one long tube, and poop comes out at the other end. Digestion starts when you chew, and spit makes food easy to swallow. Muscles in the walls of your gut squeeze food and poop along, and the squeezing is called peristalsis.

Your liver makes bile, a digestive juice that helps break down fats. Bile also gives poop its brown color. Poop is usually some shade of brown, from dark to light. Near the end of the whole long trip, the large intestine takes water out of the leftover food. What is left turns into something solid.

The last part of the large intestine is the rectum. It holds poop in until it is time to go. When it is full, nerves tell you that you need to poop. Your body makes pee and poop all by itself, but you get to choose when to go to the bathroom, and that is up to you.

Most children learn to control their bladder between ages 2 and 4, and each child learns in their own time. Wetting the bed or having an accident happens to many children. Learning takes time, and that is okay. It is almost never caused by laziness or poor toilet training. If anything ever hurts, tell a grown-up.

Pee starts in your kidneys. You have two, one on each side of your back, just under your ribs. Each kidney is about the size of a fist. They clean your blood, and they take out the waste and the extra water from it. What they filter out is water, salts and waste. That mix is pee.

Two thin tubes called ureters carry pee from the kidneys down to the bladder. The bladder is like a stretchy balloon that gets bigger as it fills. When it is full, it sends a message to your brain. To pee, its wall squeezes and pushes the pee through the urethra, the tube that carries it out of the body.

Pale yellow pee often means you have plenty of water in your body. Dark yellow pee means there is less water in it, and you may need a drink. Foods such as beets, berries and carrots can also change the color of pee, so a strange color can come from what you ate for lunch.

Words to know

• digestion: breaking down food
• peristalsis: squeezing wave
• bile: liver juice
• ureters: pee tubes
• rectum: last part

The short version

Poop is the leftover part of food that your body cannot use. Pee is waste and extra water. The large intestine turns leftovers into solid poop, and the kidneys clean the blood to make pee that waits in the bladder.

Quick facts

• Poop is the leftover parts of food that your body cannot use.
• Your kidneys clean your blood, taking out waste and extra water to make pee.
• The large intestine takes water out of leftover food and turns it into solid poop.
• Bile, a fluid made by your liver, gives poop its brown color.
• Most children learn to control their bladder between ages 2 and 4, each in their own time.