Top STEM Toys: Science, Math, and More

A 1-inch-wide R2-D2 look-alike teaches the basics of coding and robotics. Kids use the included cards or their own markers to create color-coded paths (a sequence of blue-black-blue dots makes Ozobot go faster, for example). You can also download free apps that let the 'bot follow lines on your tablet screen. iOS and Android. Ages 8 and up $49.99, ozobot.com

These electronic sets, first launched in the U.S. in 2000, were STEM-friendly before STEM was cool. Each of the more than 30 kits allows kids to snap together components to form circuits (hence the name). Among the tester favorites were kits featuring fans that blow and buzzers that beep. Ages 6 and up Starting at $19.95, snapcircuits.net

Red and blue make purple -- and create silly spectacles when kids place a lens of each color in this kit's frames. The kaleidoscope and spinning top that come with it provide a host of other hue-changing activities. Ages 3 to 6 $29.99, learningresources.com

Kids put their engineering skills to the test, using colorful towers to construct various marble runs. Cards presenting 60 building challenges (ranging in difficulty from beginner to expert) are included. Ages 8 and up $29.99, amazon.com

This science title zooms in on the giant role that microorganisms play in nature. Millions of the little guys, author Nicola Davies reveals, can fit on an ant's antenna, and they form beautiful kaleidoscopic patterns in Emily Sutton's watercolor art. Ages 5 to 8 $15.99, amazon.com

Benjamin Franklin schools 18th-century France in the scientific method in this true tale by author Mara Rockliff and illustrator Iacopo Bruno. As the beguiling, wand-waving Dr. Mesmer thrills Paris, the American inventor tests a hypothesis to learn what's really behind the mystic's power. Ages 6 to 10 $17.99, amazon.com

David J. Smith's compelling book, illustrated by Steve Adams, shrinks huge, often overwhelming facts about the world down to a more kid-friendly scale. For example, if all of the earth's water were boiled down to 100 glasses, 97 would hold salt water. Ages 7 and up $18.95, amazon.com

After watching easy-to-follow video tutorials, kids drag and drop blocks of code to design games (including virtual food fights, a tester favorite), as well as to create art and animations, all of which can be shared with others. iOS Ages 9 and up Free

For younger kids, ScratchJr teaches sequencing and problem-solving skills. Beginning programmers arrange blocks of prewritten code to create simple games and stories. iOS Ages 5 to 7 Free

Budding engineers construct virtual bridges, learning about construction techniques (triangles are strong!), then run a simulated stress test to see if their structures hold up. iOS and Android Ages 6 and up Free, ad-free version $1.99

Explore the world of robotics through photos, videos, and interactive animations of more than 150 robots, ranging from cute dogs and smart birds to realistic (and slightly creepy!) humanoids. iOS Ages 8 and up Free

Preschoolers learn about the elements as they turn up the heat, make it rain, and adjust wind speed, then see how their changes affect the app's three cute characters. Is the pink, big-eared critter shivering? Give her a virtual coat to make her smile. iOS Ages 3 to 6 Free