Who invented the peanut butter and jelly sandwich? And how did it become one of the most famous lunches in America?

In this episode, a question from listener Leila sends us on a trip through history to find out how peanut butter, jelly, and sliced bread came together to make the classic PB&J. Along the way, we learn about the first written recipe for the sandwich in 1901, how peanut butter went from a fancy food to a lunchbox staple, and why sliced bread changed everything.

To help answer Leila’s question, we turned to our buddy Mick Sullivan, host of the history podcast The Past and the Curious. Mick loved the question so much that he made a whole episode about it—and today we’re sharing it with you.

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Why do humans usually have five fingers on each hand? And what if one day, we could grow a new finger if we lost one?

In this episode, a question from six-year-old listener Ayla sends us on a journey from tiny developing embryos to one of the most amazing animals on Earth: the axolotl. 

We talk with Dr. Jessica Whited, a Harvard-based biologist who studies how axolotls regrow their limbs - and why humans can’t do the same… for now! Along the way, we discover how our hands develop before we’re born, why evolution settled on five fingers, and axolotls might show us the way to regrow our own limbs. 

Plus: why axolotls have to live in separate tanks (hint: they’re a little too snack-happy).

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Submit a science question: https://www.sciencepodcastforkids.com/contact

In this episode, we talk to two scientists who study animal friendships, in different animals, and in different ways. We’ll hear from Karen Bales, who studies titi monkeys (AKA “fuzzy little guys”) and Annaliese Beery, who studies voles (AKA “the cutest rodents”). Get ready to discover how animal friends play and cuddle - and what they can teach us about our own friendships. 

This episode was produced thanks to a generous grant from the Greater Good Science Center. Check out their website for all kinds of awesome quizzes, information, and more!

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Listen to Tumble en Español: https://pod.link/1521514886

Submit a science question: https://www.sciencepodcastforkids.com/contact

How did Earth get created? What did our planet begin as? Why does our world exist? What started our planet? These questions take us back billions of years to learn how Earth formed in the very beginning - and then, we’ll look to a group of mysterious asteroids that might reveal how Earth became the planet it is today. 

With planetary scientist Bill Bottke, we’ll hear the incredible story of Earth’s earliest days in cinematic style. And get ready for a journey to Jupiter, where a NASA mission you probably haven’t heard of is heading, in hopes of revealing mysteries hidden in the Trojan asteroids. What could they reveal about why our planet came to host life? Listen to find out!

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Listen to Tumble en Español: https://pod.link/1521514886

Submit a science question: https://www.sciencepodcastforkids.com/contact

This is a rebroadcast of one of our favorite episodes from season 9!

Do fungi breathe? That’s what listener Alice wants to know - and we’ll find out in our punniest episode yet! We visit the Fungarium - the largest and oldest collection of fungi in the world with curator Lee Davies, who describes himself as a “librarian” of mushrooms. We’ll explore how fungi live and die, and why there’s so many species left to discover. Watch out for the zombie fungi! And beware, Lindsay and Marshall don’t hold back on the “fun guy” puns!

To support Tumble on Patreon, visit patreon.com/tumblepodcast.

Our merch store is at tumblepodcast.dashery.com.

Go here to get more details about Tumble's appearance at Lincoln Center this February 7th at 11 am! It's totally free to the public!

This is a re-broadcast of a favorite episode from 2019. We actually won our first AAAS Kavli Award for this episode, along with The Cave of the Underground Astronauts. Check it out!

Why do seals have whiskers? Listener Karah’s question dives into the wonderful world of whisker science. Robyn Grant, a self-described “whisker biologist” shares her discoveries of how whiskers work, from training a friendly seal named Moe to making slow-mo movies of super speedy “whisking.” (You will find no cuter field of research… but if you do, tell us about it!) Listen to learn about humans’ hidden whisker muscles and find out to rank whiskers like the pros!

Want to learn more about whisker science? We have more from our interview with Robyn on our Patreon podcast feed! Subscribe for $1/month at patreon.com/tumblepodcast. You can also tune in on the Castbox podcast app by tuning into our Premium Channel.

Find more whiskery educational resources on our blog, at sciencepodcastforkids.com.

If you want a t-shirt from our merch store, go check it out at tumblepodcast.dashery.com.

We’re wrapping up 2025 with a final Mailbag episode, featuring some of our longest-running Patrons! Did you know, when you sign up to support Tumble on Patreon, you’ll get a personalized message from Marshall? And if you’ve been supporting us for years, we might just call you up to chat! We’ll meet our mysterious patron, MiloSloth and his family, and learn why they love to support the show. 

Plus, why is the English language so weird? Who made PB & J a combo? And do all cats hate getting wet? We have the answers.

If you want to join Milo and support Tumble on Patreon, just go to patreon.com/tumblepodcast and pledge at whatever level you want! $1 or more gets you ad-free versions of the show, and $5 and up gets you a birthday shout out! Also don't forget about gift subscriptions, which make great last-minute holiday gifts!

Want Tumble merch? Just go to tumblepodcast.dashery.com for t-shirts, mugs, hats, tote bags, and so much more.

How do people learn — and how can a video game help us find out? In this episode, we meet cognitive scientist Charley Wu, who built the ultimate science “mod” in Minecraft! Journey into a video game world of science to discover how and why Charley used one of the world’s most popular games to follow his curiosity about how humans learn. Featuring a “braintrust” of kid Minecraft experts to explain the game to Lindsay and Marshall, and a song inspired by The Minecraft Movie.

You can learn more about Charlie, and find a transcript of this episode on the blog on our website, ⁠sciencepodcastforkids.com⁠. 

Support us on Patreon! You’ll get ad free episodes, special chances to be on the show, and of course, birthday shoutouts, when you sign up at the $5 level at ⁠patreon.com/tumblepodcast⁠.

Find out what we’re up to - from live events, merch drops, and more when you subscribe to our newsletter, on ⁠sciencepodcastforkids.com⁠. You can also follow us on ⁠Instagram⁠ and subscribe to our ⁠YouTube.⁠

Try finding awesome shirts and other stuff on our merch store: tumblepodcast.dashery.com

Why do we have snot? Do animals get stuffy noses, too? We delve into the world of thick secretions with the help of Dani Rabiaotti, zoologist and author of “Believe it or Snot: The Definitive Field Guide to Earth’s Slimy Creatures.” You’ll find out why we make so much mucus, and meet the slimiest animals on the planet. Plus, you’ll discover why scientists study slime, even though it’s super gross.

This is a rebroadcast of one of our favorite episodes from season 5, inspired by a question we recently got from our listener Harrison, who wondered why snot exists. Hopefully this answers the question for him!

If you want to support Tumble with your holiday shopping, there are lots of ways to do it!

Our merch store can be found at Tumblepodcast.dashery.com

You can join our Patreon at patreon.com/tumblepodcast, or give a gift subscription at Patreon.com/tumblepodcast/gift.

Or, click our affiliate link at bit.ly/tumblemel and get some awesome science kits while helping support the show!

What sounds do fish make? 🐟🎶 We know that cows say moo, and sheep say baa, but what do fish say? Come explore “Under the Sea” to discover the chorus of fish noises with help from fish ecologist Audrey Looby.  We’ll find out how fish can be sneaky, loud, and even “slimy, grumpy cuties” (Audrey’s words) who go boop boop - and what they can tell us about life underwater. 🌊

You can learn more about Audrey, and find a transcript of this episode on the blog on our website, sciencepodcastforkids.com. 

Support us on Patreon! You’ll get ad free episodes, special chances to be on the show, and of course, birthday shoutouts, when you sign up at the $5 level at patreon.com/tumblepodcast.

Find out what we’re up to - from live events, merch drops, and more when you subscribe to our newsletter, on sciencepodcastforkids.com. 
You can also follow us on Instagram and subscribe to our YouTube.