What happens to your lunch after you eat it? As you read this, your digestive system is hard at work, taking it on a wild ride through your body. See more »

Vestigial organs are like the contents of your junk drawer: an assortment of objects that once had a purpose or might come in handy. What can these evolutionary mementos tell us? See more »

Light is what drives life. It’s hard to imagine our world and life without it. The sensing of light by living things is almost universal. Find out all about the amazing inner workings of the human eye. See more »

Does the appendix serve any purpose in the human body? Scientists are divided on the issue -- learn why. See more »

The heart is a vital organ that basically serves as a pump. Learn about heart chambers and valves, blood flow, the heart's electrical system and blood supply. Read more about how this amazing organ works. See more »

There are millions of bacteria, microbes, viruses, toxins and parasites that want to invade your body. And they'd happily do it, too -- if it weren't for your immune system. See more »

The kidneys spend 24 hours a day, seven days a week filtering gallons and gallons of blood. But that's not all these little bean-shaped organs accomplish in a day. See more »

You breathe in and out anywhere from 15 to 25 times per minute without even thinking about it -- it just happens naturally. Learn all about your lungs, various conditions and diseases, and what makes the breath of life so crucial. See more »

Despite what people say, the tongue isn't your body's strongest muscle. But you do depend on it for eating, tasting and speaking. See more »

People expel gas by either burping or flatulating. Although it's an embarrassing thing to have happen, it's also a necessity. But what would happen if you just couldn't pass the gas? See more »