The smell of Play-Doh. Everyone remembers. When people grab a glob of the stuff, even after 20 years, the first thing they say is something like: "The smell of childhood in the palm of my hand." Then they squish-squish-squish. They can't stop.

We remember what we smell, what we feel, what we hear. The oily bouquet of an Erector set. The feel of Etch-a-Sketch knobs. The sound of a bouncing red rubber playground ball. In childhood, every new sensation becomes a memory etched on our brains. Some stay, some fade. Toys, the objects of much childhood time and affection, are hold-in-your-hands conduits from the past to the present. They are memory tunnels.

"I always tell people that, if they're having trouble remembering their childhood for any reason, I say, Go to a toy fair,' " says Andrew Stanton, one of the screenwriters for "Toy Story," the 1995 movie at least partially responsible for the recent sales boom in Hot Wheels, Mr. Potato Head and other old toys featured in the animated film. "You'll see so many toys you forgot you had, and so many memories will come flooding back, you'll be a ball of mush by the time it's over. You'll be in a fetal position in the parking lot."

I wasn't expecting a catharsis when I went to the U.S. Patent and Trademark Museum in Crystal City yesterday to preview an exhibition: "The Art of the Toy," which opens today. I remembered all my toys: GI Joe with the kung fu grip. Yellow Tonka trucks almost as big as I was. Battleship. Lincoln Logs. Tinker Toys. Above all, Hot Wheels -- those cool little cars with the springy wheels, the catapult start and the endless, beautiful, extruded orange vinyl track. I remembered these as well as I remembered my childhood. I just wanted to see them again.

The exhibit is small, but comprehensive. Filled with borrowed and bought toys and swag rummaged from basements, the show starts with turn-of-the-century metal trucks, Raggedy Anns and an authentic Teddy Bear, named for the only animal, perhaps, that Teddy Roosevelt didn't shoot. It includes some fascinating drawings of toys submitted for patents. One is a 19th-century inflatable fright wig, with hair follicles that stand up when air is pumped into them via a hose connected to a hand-held bladder.

There are some patents that, understandably, did not catch on in the market. One ill-advised proposal, from 1945, depicted a ship that, when a bomb-shaped projectile was dropped on it, flew apart in a mock explosion. It was frighteningly reminiscent of the USS Arizona at Pearl Harbor, just four years removed. Hours of fun for the war baby.

The exhibit's curators, Paula Coupe and Dominic Simone, said they had weeks of fun accumulating the toys, then researching their past and displaying them. Coupe is a Patent Office spokeswoman and Simone a patent examiner, but both have done an admirable job as archivists.

"See that?" says Coupe, pointing to a stack of geometric figures sketched in colored pencil by a Spirograph. "I did those last night. Aren't they pretty?" Her voice had the same tone as a child proudly presenting a drawing to be displayed on the refrigerator. The exhibit continues up through the present, including CD-ROMs that have received patents -- even some that allow the viewer to play traditional games such as Monopoly. (CD-ROM Monopoly? How could you hide that secret $500 under the board?)

The exhibit's one drawback is that it is exactly that: an exhibit. These are items that are begging to be touched, hugged, thrown, loved. So much of the appeal of toys is tactile and it is frustrating to see these beloved items and not be able to touch them.

Some of the toys on display are considered classics by manufacturers, which is to say they endure from generation to generation. Barbie is the foremost example. The doll with the exaggerated figure, which has been accused of promoting unreal body images in girls, has been a mainstay since it was introduced in 1958. But sales have jumped from $43 million in 1987 to $1.4 billion last year, according to Mattel, maker of the doll. Toy analysts say much of the bump is because baby boomer mothers, who loved Barbie as girls, are buying them for their daughters.

A similar pattern is happening with many '60s and '70s toys. GI Joe, introduced as a mighty, foot-high warrior in 1964 with a scar on his right cheek that hinted at mystery and history, was a staple of boys' toy boxes. He had all those neat things: machine guns, hand grenades, a scuba outfit, something that looked like a frog gig. He defined a time in American history.

"I'm paraphrasing a book I just read, but GI Joe was very much a product of the Cold War," says Stanton, the screenwriter. "You didn't fight with GI Joe. You planned with him. You prepped with him. You could pose him." Just like the Cold War between the United States and the Soviet Union: no warhead-to-warhead fighting, just lots of posing and planning.

In 1976, as plastic costs increased and sales almost disappeared, GI Joe shrank to about six inches tall; downsized, emasculated. He was no longer GI Joe. He was more like GS-9 Joe. But the retro toy boom has brought him back to full height, marketed under the Classic GI Joe label.

Hot Wheels, introduced in 1968 by Mattel, have undergone a similar resurgence. The Hot Wheels logo -- an orange-and-red flaming race wheel -- is a pop culture icon to a generation of children. It said "cool" like nothing else. Still does, apparently, from the looks of the high school waifs at rock clubs who use the tire-shaped Hot Wheels carrying case, no doubt pillaged from dad's old toy box in the attic, as a purse.

In a toy store a few days ago, I struck up a conversation with a guy frantically grabbing Hot Wheels cars, tracks, anything he could get.

"For your son?" I asked. "Oh, yeah," he said. "Did you have Hot Wheels?"

"Sure. We used to run them from the living room into the dining room. Remember the loop-the-loop?"

How could I not? It was the signature element of any self-respecting Hot Wheels layout.

"My wife was telling me what our son wanted, like, He wants this and he wants that,' " he said. "But I said, Oh, no, honey. He'd much rather have Hot Wheels.' "

Toward the end of the Patent Office exhibit, after the Barbie but before the Pong (remember Pong, the early video game?), I stopped, frozen in place like a green plastic soldier on its base. At first I didn't recognize it. Then I looked again: It was the lunar surface station of Major Matt Mason, Mattel's Man in Space.

How could I have forgotten?

I loved my Tonka trucks. I loved my GI Joe. I could even draw diagonally with my Etch-a-Sketch, which was no mean feat. But I had completely forgotten the most beloved toy of my youth: Major Matt, sort of a proto Buzz Lightyear.

The Major was about six inches tall and wore a white spacesuit with black accordion flexes at the joints. He had a 3-foot-tall space station with white plastic floors and orange plastic girders. The coolest part was the control room on top, a hexagon surrounded by fold-down, blue-tinted plastic. And the accessories! A space crawler to explore the moon's surface, powered by about a dozen D-cell batteries. A space cannon. A Reconojet Pak.

Why did the Major mean so much to me? Because I was an Apollo baby. I made models of Saturn rockets. One of my earliest TV memories was being allowed to stay up past my bedtime and watch Neil Armstrong set foot on the moon at 10:56 p.m. EDT, July 20, 1969. The Major represented the idealism of childhood and American can-do-ism. If we had put a man on the moon in 1969, just eight years after President Kennedy commanded it, surely Major Matt's moon station would be a likelihood within a few years. I was sure I was going to be an astronaut. But then I grew up. I found out that being an astronaut is hard. NASA's next big deal was Skylab, sort of a double-wide trailer in space that ignominiously burned up in re-entry years later instead of voyaging to new worlds. I gave up my dream of being in space, of experiencing zero gravity. It all seemed impossible, when, just 25 years ago, everything seemed possible. Maybe that's why I forgot Major Matt. Until yesterday. The U.S. Patent and Trademark Museum is at 2121 Crystal Dr. in Crystal City. Hours are 8:30 a.m. to 4:30 p.m., Monday through Friday. "The Art of the Toy" will be on display for six months. CAPTION: At the U.S. Patent and Trademark Museum, Barbie brings back childhood memories in an exhibit on toys. CAPTION: At the U.S. Patent and Trademark Museum in Crystal City, memories are made of these: Toy trains and Lincoln Logs.