Have you ever met a microbe?

You bet you have! They're in the air and on your skin. They're in your bed, in your kitchen sponge, in the food you eat and the water you drink. They're even inside your body!

You don't normally get to look at them, though, because microbes are so small that they can only be seen through a microscope. Another way to see them is to visit a new exhibit at the Smithsonian Institution's International Gallery in Washington. The show, "Microbes: Invisible Invaders, Amazing Allies," opened last week and continues through September 6.

The exhibit uses video games, 3-D animation, computer graphics, virtual reality and hands-on activities that make learning about microbes fun. Visitors can look through microscopes, play video games, participate in quiz shows and much more.

"Visitors meet the good, the bad, and the ugly of the microbial universe," says Randall E. Kaye, director of pediatric health at Pfizer Inc., the pharmaceutical company that is sponsoring the exhibit.

The microbe is the smallest form of life on Earth. Although most microbes are harmless, some cause serious illnesses while some others are useful.

You probably know them by their nicknames, "bugs" or "germs," but microbes fall into three scientific categories:

Virus. These are the tiniest microbes. which may be as small as a millionth of an inch across. Viruses live by injecting their genes into cells to produce thousands of new viruses. Certain viruses cause illnesses such as the flu, the common cold, chicken pox and measles, as well as life-threatening illnesses such as AIDS.

Bacteria. These microbes may be 125,000th of an inch across. Bacteria live by producing their own food or feeding on live hosts or dead matter. Certain microbes can cause illnesses such as strep throat and tuberculosis.

Fungus. These microbes live by decomposing, or breaking down, other matter. There are about 100,000 kinds of fungi, including mold and mildew. In nature, fungi break down matter such as dead leaves into nutrients that plants and animals reuse. But some fungi can cause health problems such as athlete's foot.

You've probably figured out by now that certain microbes are bad guys. Knowing that they're there, mostly just hanging around but sometimes causing illnesses, may make you be a little more careful about using hot water and soap the next time you wash your hands!

But there are lots of helpful microbes as well. Some are used to consume oil in oil spills. Other microbes create yogurt and cheese. Without microbes, you couldn't digest your food. Millions of microbes inside your stomach and intestines break down food into nutrients that your body can use.

If you visit the Smithsonian exhibit, you'll come across one of the major good-guy microbes in the form of an three-dimensional hologram floating in midair. The hologram is an image of a microbe that has saved millions of lives over the years. It's a fungus called penicillium.

Does the name sound familiar? In 1928, a doctor discovered that the fungus had the ability to kill bacteria. That discovery led to the development of the first antibiotic in 1943. What was the name of this miracle drug, which could cure diseases such as pneumonia and meningitis? Penicillin!

Visitors to the Smithsonian exhibit will go away seeing the world a little differently, Kaye says.

"There's an invisible world out there," he adds. "Microbes are around us all the time, living and breathing, just like we are."

Tips for Parents

To get the most out of a visit to "Microbes: Invisible Invaders, Amazing Allies," children should experience the exhibit with their parents, suggests Randall E. Kaye, director of pediatric health at Pfizer Inc. "It's an opportunity to get some good discussions going about how to stay healthy," he says. To make that easier, several Smithsonian museums will remain open later in the evening for "Science Summer Nights." The extended hours offer families more time to enjoy the many science exhibits on the Mall. The extended hours began last weekend and continue through Labor Day. The International Gallery (site of the microbes exhibit), National Museum of Natural History, and National Museum of American History will all be open from 10 a.m. until 7:30 p.m. daily. The National Air and Space Museum will be open from 9:30 a.m. until 6 p.m. daily.

For You to Do

If you ran a museum, what would you put in it? Pretend that you have been asked to create an interactive exhibition to help kids stay healthy. What kinds of things would you include? Would there be games and activities for kids? What would they be like? Make up a name for your exhibit and then draw a poster advertising it.