Today we were wondering about feelings. It’s fun to have good feelings, like the excitement you feel when you realize the end of the school year is a few weeks away. But sometimes we have bad feelings, too.

We talked about grief, the feeling you get when you lose something, or when someone close to you goes away. Why do we have feelings like grief? Wouldn’t it be better if we never felt bad? After talking about it for a while, we decided that grief has a purpose — it reminds us to value and love our family and friends while they’re with us.

Throughout history, people have wondered about their feelings. Poets and philosophers try to make sense of how we feel. But there are also scientists who investigate the way people feel. These scientists are called psychologists. Some psychologists are like doctors for your feelings; they try to help people who feel bad. Other psychologists do research to figure out why people feel different ways in the first place.

Like most mammals, people have hair over most of their bodies. We aren’t covered with fur all over our bodies like animals are, and scientists think that people today have less hair than primitive humans did. Because of the way that creatures change over time, humans born today have less hair than they did thousands of years ago. But scientists don’t really know why this is — having less hair probably didn’t make it easier for ancient humans to survive.

It’s possible that people decided long ago that humans with certain kinds of hair were just more beautiful, and so those kinds of humans had more babies that looked like them.

Although you have hair on most of your body, some of it is too fine to see. Two places where you don’t have any hair are the palms of your hands and the soles of your feet.

Do you notice that adult men usually have more hair on their bodies than women? Adult men grow hair on their faces and on their upper bodies, while women do not. It’s possible to remove hair from your body by shaving it off.

Children don’t have much hair on their bodies (except for the hair on your head, of course). But as you grow older, your body will gradually change and you’ll grow more hair on different parts of your body. By the time you finish high school, your body hair will look more like what you see on an adult’s body.

People and most animals have tongues. Your tongue is good for three things:

• Helping you eat food
• Helping you taste food
• Making funny faces

We taste food with our tongues to see if the food is good to eat or not.

Did you ever notice that your tongue is bumpy? The bumps you feel on your tongue are called taste buds. They’re the part of the tongue that lets you taste things.

You have about ten thousand taste buds on your tongue. There are different kinds of taste buds for different kinds of tastes: sweet, salty, savory, bitter and sour.

When you take in a breath, what happens? If you take a big breath, you can feel air going into your body through your mouth. But why do we breathe? We breathe because our bodies need something in the air called oxygen. Oxygen is like food for our blood. You can’t see oxygen, but it’s there in the air, and people and animals need it to live.

Your body changes oxygen into a different gas called carbon dioxide. Carbon dioxide is what comes out of your body when you breathe out. You breathe in oxygen, and you breathe out carbon dioxide.

Trees and plants don’t breathe oxygen as we do. They take in carbon dioxide and they put out oxygen — just the opposite of people and animals. So having lots of plants around is good for people and animals — plants and trees make the oxygen that we need to breathe.

Doctors know a lot about how to help people who are sick or injured. But how do they learn how to help people? It takes years of special schooling to learn how to be a doctor. In medical school, doctors learn about peoples’ health from books and classroom discussions, but they also learn by doing experiments, just like other scientists.

To really learn about what’s inside our bodies, student doctors sometimes cut up dead bodies. Bodies that are used by student doctors are called cadavers. Before they die, people sometimes give permission to medical schools to use their bodies to teach doctors. Cutting up a dead body may seem gross, but doctors become accustomed to it. Using cadavers is the best way for a doctor to learn what goes on inside our bodies.

You’ve probably noticed that sometimes when you cut yourself, blood comes out. But what is blood, and why does it come out when we cut ourselves?

Blood is made of many different parts. These parts of the blood are tiny — smaller than you can see. One part of blood is made of red blood cells which carry the air you breathe throughout your body. Red blood cells also give blood its red color.

You can see what blood cells look like under a microscope in the picture at right. (Because this picture was taken by a microscope, which makes tiny things look much larger, the cells look bigger than they do in real life.)

When you get a cut, sometimes tiny creatures that are too small to see can try to get inside your body through the cut. If some of these creatures get into your body, they can cause an infection, which makes the cut hurt a lot more. Your blood helps keep those bad creatures out. There’s another part of your blood, called white blood cells, which help keep the bad guys out of your body. Like red blood cells, white blood cells are also too tiny to see. The job of a white blood cell is to prevent bad creatures from coming into your body through a cut and infecting you.

Whenever you cut yourself, you should get help from an adult (like one of your parents or a teacher) to clean the cut and put a bandage on it.

Getting a cut is no fun, and you probably don’t like to see blood come out when you cut yourself, but remember that the blood is there for a good reason.