After you eat a meal, your body embarks on a long process of digestion and absorption. The stomach breaks down food, and the small intestine absorbs most of the nutrients, vitamins, and minerals. But what happens to the parts that can't be used?

This leftover material moves into the large intestine, where it becomes feces. Feces are the solid or semisolid remains of food that your body couldn't digest. Think of it as the final waste product of the digestive process.

You might be surprised to learn that feces are not just undigested food. They have a complex composition that tells a story about your body's inner workings. About 75% of feces is simply water. The remaining 25% is a mix of solids.

The rest is a combination of:

• Indigestible food: Mostly dietary fiber, like the tough parts of plants.
• Metabolic waste: This includes substances like bilirubin, a pigment that comes from the breakdown of red blood cells. Bilirubin is what gives feces its characteristic brown color.
• Cellular lining: Your body sheds cells from the lining of your intestine, which become part of the waste.

The journey from leftover food to feces happens in the large intestine, also known as the colon. As the waste material moves through the colon, water is gradually absorbed back into the body. This process solidifies the waste.

Once formation is complete, the feces move into the final section of the large intestine: the rectum. The rectum acts as a temporary storage area. When it stretches to a certain point, it sends a signal to your brain that it's time to go to the bathroom. This triggers the urge for defecation, the act of expelling feces from the body.

This process is controlled by two sphincters in the anus. The internal sphincter relaxes automatically when the rectum is full. The external sphincter, however, is under your voluntary control. This allows you to decide the appropriate time and place for defecation.