Barbara and her cousin Cathy went to Girl Scout Camp together. They had a great time swimming, hiking and putting on a camp show. They were away from home for two weeks, which felt like a really long time.

Sometimes in their bunks at night they felt homesick. Once or twice they cried a little as they fell asleep. Even though crying felt sad, the two campers always felt a little better afterward.

Toward the end of camp, the cousins began to get excited about getting home. They felt like the last night of camp would never come. When it did, they sat around a big campfire singing songs and toasting marshmallows.

A surprising thing happened: even though the campers were anxious to get home, they started feeling sad about leaving camp. As they sang the last song of the evening, many of the Girl Scouts were in tears. The teenaged junior counselors were sniffling. And the grown-up counselors were crying too!

Crying is something that all human beings do. We cry when we're sad, and when we're happy. We cry when we're scared, or when we're angry.

Researchers at the University of Minnesota have studied human tears. They collected the tears in two ways: they showed sad movies, and gathered tears people cried. They also collected tears people shed after they smelled raw onions.

When they examined the tears, they discovered that the two types of tears contained different chemicals. Emotional tears -- those caused by feelings -- were made from one set of chemicals. But physical tears -- the kind we shed when our eyes are irritated by pollen, raw onions or from a cold -- contained different chemicals.

The researchers found out that the chemicals in emotional tears are similar to substances the body makes to fight pain. Tears also contain chemicals the body produces when it's under stress.

The University of Minnesota researchers hope to find out more about tears. What they have discovered so far suggests that our bodies use crying to get rid of chemicals that build up when we feel very strong emotions. So it looks as if people are right when they say "Have a good cry. You'll feel better."

As you probably know from observing your own families, children aren't the only people who cry. Adults cry too.

After studying 200 adults, the University of Minnesota researchers reported that a typical grown-up man cries about once a month. A typical adult woman cries about five times a month. Nearly all the women and three quarters of the men in the study said they felt better after crying.

Even when you aren't feeling strong emotions, your eyes produce tears. They just down spill over. But you always have some moisture in your eyes.

A small sac found under the top lid of each eye produces the tears. These tear glands make a mixture of water, salt, and mucus. The mixture bathes your eyeball, and helps keep it clean and healthy.

Each time you blink, your eyelids work like windshield wipers. They swoosh the tears across your eye, killing germs and keeping the area from drying up.

Normally, tears drain into your nose through tiny holes at the corner of your eyes called tear ducts. When something unusual like raw onions or pollen irritates your tear glands, they produce more liquid than normal. The tiny tear ducts can't drain all the tears away, so they flow onto your cheeks.

And the tears are helpful. They wash away irritating chemicals, or flush bits of dirt out of your eye.

When you feel strong emotion your brain signals your tear ducts to produce extra fluid. You burst into tears. Most of the tears spill out onto your cheeks. The rest drain through your tear ducts into your nose. That's why you often have to finish a crying spell by using somebody's handkerchief to blow your nose.Tips for Parents

Tears can be a healthy release for children as they undergo the stresses and strains of everyday life. But some babies and small children may cry so often and for so long -- especially at bedtime -- that their parents seek help.

At Fairleigh Dickinson University in Hackensack, N.J. a Crying Baby Clinic helps parents whose children cry excessively. Geared for kids up to age 4, the clinic offers counseling on dealing with the problem.

After ruling out physical ills, such as food allergies, doctors at the center find that a typical case is a child who has never learned to fall asleep on its own. The center counsels parents to put these children to bed, and leave the room while they are still awake.

If crying starts, wait five minutes before returning. If the child still cries, increase the time between visits to the room by five minutes until the child falls asleep. It's crucial to always leave the room while the child is still awake. That way, the child begins to learn that sleep will come even if he or she is alone.