GERMS: the ultimate superheroes. They're fast, aggressive and amazingly accurate. Seen in this way, the hidden life of germs is a wonderland tailor-made for kids' imaginations, which is what the Smithsonian has discovered with its exhibit "Microbes: Invisible Invaders . . . Amazing Allies."

Positioned before a video game called Antibiotic Artillery -- one of several interactive features of the exhibit -- Andrew Metcalf has a firm grip on the joy stick, firing off shots at invading bacteria. "Most museum exhibits are kind of boring, but this one's fun 'cause it's virtual reality," says the Potomac School fourth-grader, not moving his eyes from his target. What has he learned so far from this exhibit? Andrew looks up with a broad grin.

"Most microbes are good but some are bad," he says. "And as soon as the good ones see a bad one, they go right after him."

Andrew is right -- about many microbes. There are those that make us sick and those that keep us healthy, as the exhibit makes clear. It's a microbial monument, a small-scale germ theme park, with a talking robotic figure, holographic images, video games, a gabbing kitchen and a virtual combat zone. But the displays and games also aim to teach about the bacteria, viruses, fungi and protozoa that have infected, itched and generally grossed out humanity for eons. They also shed light on the nice ones that create yogurt and fight diseases.

It's probably best to prepare young children for the decidedly grim entrance to the exhibit, where the point is made that microbes have been with us since the dawn of time. You're plunged into near-darkness in what is supposed to be a Paris crypt, where you come face to face with a tombstone erected to the bubonic plague. The notorious Black Death -- caused by a type of bacterium spread by fleas -- killed about 56 million Europeans in the 14th and 15th centuries.

Around the corner lurks Dr. Medieval, a mechanical representation of the medicine man typical of the era, who wears a large hooded mask filled with posies, or dried flowers, thought to ward off the poisoned gas that was blamed for the disease. (My 5-year-old was quite spooked by the talking robot and even on repeat visits has wanted to scoot past these first few rooms.)

You then move quickly into better lighting, entering an Egyptian tomb and passing replicas of Aztec ruins, which demonstrate the mark that infectious diseases left on those cultures. A photo of Ramses V's mummified face bears evidence of the smallpox infection thought to have killed him in 1151 B.C.

For adults, what is likely to be the most moving -- and tragic -- portion of the exhibit is called Main Street North America, which documents polio, flu and tuberculosis epidemics here at home. There's a child-size iron lung from the 1950s, and behind it a wall-size photo from the period shows rows of small children encased in such machines, with only their heads protruding, attended to by nurses. The sad truth is that most of them likely succumbed to the paralyzing illness; once it had disabled their lungs, the machines only bought them a bit of time.

After passing by these glimpses of history, the fun begins. Spacey, wispy music greets visitors in a black-lighted room, the "Microbial Universe," where you've suddenly "shrunk" to the size of a microbe. The walls and ceiling are plastered with huge models of glow-in-the-dark germs, some fuzzy, others round and smooth, or with long creepy legs. Two huge bugs the size of armchairs -- a protozoa, or parasite, and a bacteria -- preside over what seems to be a big germy circus.

There are even aerial displays -- microbial holograms, shimmering and whirling slowly in space, if you stand at just the right angle. From a certain perspective, they're quite . . . stunning.

"Viruses tend to be very beautiful, very crystalline, as opposed to protozoa," says Randall E. Kaye, the director of pediatrics at Pfizer, the pharmaceuticals company that is one of the exhibit sponsors. "Like that giardia." He points to a beige slug-like form with legs. "That looks pretty scary. I don't think anything's as pretty as the influenza virus."

He has a point. It is striking, a rose-colored sphere studded with tiny sparkling lights.

The kids gleefully try to grab the holograms, grasping in vain at the dancing images of HIV, salmonella and penicillin (which is -- surprise -- a type of mold). There is also a pair of large microscopes through which you can look at such things as bread mold or dog hair. (Okay, so you might not want to look. But your kid will.)

The noise flooding from the next room alerts you to the interactive games there. It's a kind of viral video arcade, with games that show how swiftly microbes race through the body, or how certain ones can be used to gobble up an offshore oil spill. There's a foosball game called "Lines of Defense," where one team is Hair and the other is Skin, and they're kicking around a microbe. Hugely popular is the "Virtual Invaders" game, where a child can stand in front of a screen and swat away the germs that start to bombard her video image. (Even my 2-year-old clamored to have a turn.)

In Pete's Place, a modified kitchen, kids can open up the refrigerator and oven doors to hear such things as the cottage cheese talking about its necessary bacteria (you can't quite make out what it's saying, but then you wouldn't expect cottage cheese to articulate, would you?)

What this exhibit proves is that even a sophisticated subject like the invisible microscopic world can be made fun and accessible for children. By popular request, I've taken my sons back several times. I can't prove that they're washing their hands any more frequently, but when I catch them trying to duck the habit, all I have to say is, "Remember the Microbes exhibit? Germs all over the place?" And I think they understand.

The exhibit ends with a call to action, alerting visitors of the modern microbial dangers posed by overcrowding, pollution and poor control of the water supply. There's a good deal of Pfizer rah-rah, too, with displays of how much it costs to create a new drug, etc. Of special interest is a display case bearing an original mold (one of only two in the world) from Sir Alexander Fleming's 1928 discovery that led to the manufacture of penicillin.

To underscore the lessons presented here, kids can pick up a free Microbe Mission Action Guide comic book and a pamphlet on ear infections. And undoubtedly they'll leave with an opportunistic germ or two -- or 2 million -- but then, they could pick those up anywhere.

MICROBES -- Through Sept. 6 at the Smithsonian's International Gallery, S. Dillon Ripley Center, 1100 Jefferson Dr. SW (Metro: Smithsonian). 202/357-2700. Web site: www.pfizer.com/rd/microbes. Open 10 to 7:30 through Sept. 6.

In conjunction with this exhibit, the Smithsonian's Discovery Theatre performs two shows on the same floor of the Ripley Center Tuesdays through Saturdays. "The Marvelous Musical Microbes," for ages 2-6, runs at 11 a.m. and noon. "One Step Ahead," for ages 6-12, runs at 2 and 3 p.m. Admission is free. No reservations necessary.

Also in connection with this exhibit, "Summer Science Nights at the Smithsonian" means later evening hours at several museums. The National Museum of American History, National Museum of Natural History and the Smithsonian's International Gallery will stay open until 7:30 p.m., and the National Air and Space Museum will stay open until 6 p.m. through Sept. 6.

CAPTION: The Microbial Universe captures the attention of two children.