Ask scientists of a certain age about their childhood memories, and odds are they’ll start yarning about the stink bombs and gunpowder they concocted with their chemistry sets. Dangerous? Yes, but fun.

"Admittedly, I have blown some things up in my time," said William L. Whittaker, 64, a robotics professor at Carnegie Mellon University who unearthed his first chemistry set, an A.C. Gilbert, in a junkyard around age 8. By 16, he was dabbling in advanced explosives. "There’s no question that I burned some skin off my face," he recalled.

Under today’s Christmas tree, girls and boys will unwrap science toys of a very different ilk: slime-making kits and perfume labs, vials of a fluff-making polymer called Insta-Snow, "no-chem" chemistry sets (chemical free!), plus a dazzling array of modern telescopes, microscopes and DIY volcanoes. Nothing in these gifts will set the curtains on fire.

"Basically, you have to be able to eat everything in the science kit," said Jim Becker, president of SmartLab Toys, who recalled learning the names of chemicals from his childhood chemistry set, which contained substances that have long since been banned from toys.

Some scientists lament the passing of the trial-and-error days that inspired so many careers. "Science kits are a lot less open-ended these days," said Kimberly Gerson, a science blogger who lives outside Toronto. "Everything is packaged. It’s either ‘yes’ or ‘no.’ If you don’t get the right result, you’ve done it wrong and you’re out of chemicals."

Others, though, say the new crop of science toys — even with their cartoonish packaging and heavy emphasis on neon goo — actually represent progress. More entertaining, educational and accessible than earlier products, which relied heavily on a child’s inner motivation, these toys may actually help democratize the learning of science and introduce children to scientific methods and concepts at an earlier age.

"I grew up in the 1960s, and a lot of the chemistry sets were kind of boring," said William Gurstelle, a science and technology writer. "You’d go through the book, and at the end of the experiment you’d get some light precipitate at the bottom of the beaker. Maybe at most it changes color or something."

Gurstelle’s books, which include "Whoosh Boom Splat" and "Backyard Ballistics," teach people how to make dangerous projectiles, like a potato cannon that uses hair spray as launching fluid. But he had high praise for commercial science kits, which show children (among other things) how to make slime.

"Well, that’s a pretty cool thing to have when you’re done," Gurstelle said. "You’re not going to really learn to be a chemist from a chemistry set when you’re in seventh grade; you’re just going to be inspired. The point is that new chemistry sets and new toys are just better, because the manufacturers have figured out how to make them more fun."

Some toy makers, like SmartLab, Becker’s company, have used this philosophy to give some classic toys a modern makeover. One of SmartLab’s takes on a chemistry set, for instance, is the Extreme Secret Formula Lab, which comes with "squishy-lidded bubble test tubes" and "an abundance of glow-in-the-dark powder." The game of Mousetrap has been re-envisioned as the Weird and Wacky Contraption Lab, which lets children release their inner Rube Goldberg. And the slot car tracks that Becker recalls snapping together in his youth have been translated into a robot called ReCon 6.0, which children can program to roam around.

"What we do is give kids the opportunity to learn through problem solving," Becker said.

Of course, computer technology has also remade the experience of learning science. Children may be more likely to click on a science app than go and play outside.

Critics of the new toys say that’s all the more reason to promote playthings that are more suggestive than prescriptive, items that evoke creative thinking. Will the Beautiful Blob Slime Lab release your child’s inner chemist?

"I think back to when you had a bucket of Legos dumped in front of you, and you could do what you wanted with them," said Gerson, the science blogger.

Certainly, science toys have evolved. In the 1920s, ’30s and ’40s, Erector Sets and chemistry sets with real glassware, chemicals and spirit lamps were "meant to breed a scientific culture in America," said Art Molella, a science historian who directs the Smithsonian’s Lemelson Center for the Study of Invention and Innovation. The atomic era of the 1950s and the launching of Sputnik ushered in science kits that pointed out the possibilities in energy and space, including some with samples of real radioactive ore. For better or worse, Molella said, "there was a lot of hands-on aspects to it, not like our video games today."

Those toys did indeed breed a generation of scientists. Roald Hoffmann, who won a Nobel Prize in Chemistry in 1981, remembered playing with an A.C. Gilbert chemistry set from age 11, making gunpowder from sulfur, charcoal and nitrate. "I would paint the solution in parallel lines on a piece of paper, let it dry and then ignite it," said Hoffmann, 75, a professor at Cornell. "It didn’t explode; it just burned along the path of the solution."

The thrill of such early experimentation is described in memoirs like Primo Levi’s "The Periodic Table" and Oliver Sacks’ "Uncle Tungsten." Hoffmann describes the latter book (which is dedicated to him) as "a wonderful account of how the sort of smell, stinks and color and explosions of chemistry attracted a young boy."

Today, Hoffmann added, "we over-romanticize the experience, but I think something is lost, something in the excitement. I think parents worry."

Yet the classic science toys have not completely disappeared. Many old favorites exist in modern forms. The Visible Man and Visible Woman anatomy kits have yielded shelf space to the Squishy Human Body Kit, which has rubbery internal organs and an instruction book that explains what happens when a bite of pizza is digested. "Having kids take those pieces, hold them and put them in there, they get such a deeper understanding of what’s going on than they ever could looking at a screen," Becker said.

Another iconic toy, the Ant Farm, introduced in 1956, still exists — including in a high-end version that "projects the shadows of the ants up on your ceiling," said Frank Adler, president of Uncle Milton, the company that makes it.

And classic chemistry sets, complete with mildly dangerous chemicals, are still available, largely as a boutique product. An 11-year-old company called Thames & Kosmos imports its kits from Germany, selling what are considered to be the only high-end chemistry sets in wide distribution in the United States.

"There’s a lot of people who say the great innovators of the last century all had the opportunity to play with things like chemistry sets, and had the possibility to explore things in a more open-ended way, and that’s what led to their great innovations," said Ted McGuire, president of Thames & Kosmos. "Now people are worried we don’t have those same opportunities for our young people."

But even at the goo-making end of the retail spectrum, toy company executives make good arguments for the educational value of their products. At Be Amazing! Toys, top sellers include Insta-Snow, Cool Slime ("Just mix the two liquids together and you’ve got perfect slime every time") and the Geyser Tube, which is a package of Mentos and a tube to funnel them into a soda bottle. Some kits cost under $5.

"We look at ourselves as, ‘Here’s a great way to introduce your child to the world of science and make it interesting, not boring,"’ said Renee Whitney, a vice president at Be Amazing! Toys. "Once they’ve had the ‘wow effect,’ we try to explain why it happened."

Snobs may scoff, but the experiments are quick and foolproof and can be done (whew!) without a grown-up. Science lessons are spoon-fed along with the fun: Kits like Growing Gators, which comes with miniature alligators and cards to track their growth, ask children to measure their experiments and hypothesize about what might happen, Whitney said. That sugary-looking "Water Gel" that turns water into a solid? The kit explains that it’s the same stuff found in baby diapers, and encourages children to cut open a dry diaper and see how much powder it has.

"We’re trying to teach them to think like scientists," Whitney said.

Whether a future generation of scientists will look back fondly on their days of dropping candies through the Geyser Tube into Diet Coke remains to be seen. But it does seem that each generation grows up with a science toy that inspires in a particular way.

"I’m 31 years old, and when I was growing up, everyone had this little Fisher-Price doctor set," said Rosie Cook, a historian at the Chemical Heritage Foundation who is curating an exhibit on chemistry sets. "I honestly think that’s why a lot of people my age wanted to be doctors."

THESE WERE A FEW OF THEIR FAVORITE THINGS

The asked five noted scientists about the toys they remember from childhood.

Mike Brown, 47, astronomer, California Institute of Technology, and author of "How I Killed Pluto"

I did everything with Lego blocks. We just had boxes full of squares and rectangles and made buildings and contraptions that ran down strings. We experimented with things that had wheels and pulleys. My brother and I would try to make traps we would try to spring on each other. By 12 or 13, I was blowing up things with firecrackers and calcium carbide. At one point I gave myself second-degree burns on my arms.

Maria Zuber, 54, geophysicist, Massachusetts Institute of Technology

Of course I loved my chemistry set. I played with that a great deal and mixed together toxic things and household things, probably at age 10 or 11. It had flasks and test tubes and gave you small amounts of different elements you could mix together, things that changed color. It came with little paper sheets so you could measure the pH and tell if something was an acid or a base. I’m one of those odd people who read chemistry books for fun at that age.

Jonathan Eisen, 44, evolutionary biologist, University of California, Davis, and academic editor in chief of PLoS Biology

When I was a kid, it was much more a magnifying glass and go out into the yard and look at things. We would just go out and look at ants and roly-polies. Being able to see things close up was very cool. With our children (ages 5 and 7) we rear painted lady butterflies and chrysalises and eggs and watch them hatch into caterpillars. Silkworms, too. They are voracious eaters.

Nancy Hopkins, 69, biologist, Massachusetts Institute of Technology

A favorite toy for years was a construction set with metal pieces and magnets, all in bright colors that you could build things with. There were flat metal pieces and magnets of different strengths and sizes and everything in a different color. My mother was an artist, and we used to go every weekend to the Museum of Modern Art. I loved modern art. I liked Kandinsky. These magnets reminded me of him. I can still remember being dragged screaming from it at bedtime, and recall the feel of the pieces.

Jane Lubchenco, 65, administrator of NOAA and undersecretary of commerce for oceans and atmosphere

The stereotypical science toys like microscopes and Erector Sets never really sparked my imagination. I was much more enamored with the outside world. I grew up in the 1950s in Colorado, and we spent a lot of time in the Rockies hiking and fishing. I was a veteran collector. I went through a wildflower phase and a rock phase. I was a Girl Scout for many years, and pretty much every outdoor science badge you could do, I did.

— LAURA GEGGEL

© 2012 The New York Times Company