Are you afraid of the dark? It’s OK to be a bit scared of things that go bump in the night. But what about things that glow at night?

You’ve probably seen or played with glow-in-the-dark toys before. From yo-yos and balls to stickers and stars, glow-in-the-dark toys can turn any dark room into a magical world of adventure!

Have you ever WONDERed how these things glow in the dark? Guess what? It’s not magic! It’s just plain and simple science.

Glowing in the dark — also known as luminescence — simply requires chemicals that store energy when exposed to light. These special substances are called phosphors. This type of glowing is sometimes called phosphorescence.

Phosphors radiate visible light after being energized. This means you have to expose the items to light for a while before they will glow in the dark.

Phosphors then slowly release their stored energy over time. As they release the energy, they emit small amounts of light, which we see as an object glowing.

Sometimes glow-in-the-dark objects will only glow very weakly for a short time. Often, you have to place them in a very dark place to see their faint green glow. Newer glow-in-the-dark items may glow more brightly for several hours.

Over the years, chemists have created thousands of chemical compounds that act as phosphors. For glow-in-the-dark toys, manufacturers look for phosphors that can be energized by normal light and that glow as long as possible.

To make glow-in-the-dark toys, manufacturers mix their chosen phosphor into plastic and then mold it to the desired shape. Two of the most common phosphors found in glow-in-the-dark toys are zinc sulfide and strontium aluminate.

There are a couple of other types of luminescence. Chemiluminescence, for example, makes object glow in the dark because of a chemical reaction. When two particular chemicals react, they produce energy that is subsequently released, creating a glow. This is what happens in glow sticks.

Radioluminescence uses phosphors that are constantly charged by adding a radioactive element, such as radium, to them. You may have seen this type of luminescence on the hands of a watch, for example.

One final example from nature is bioluminescence. Some creatures, such as fireflies and jellyfish, contain chemicals within them that cause them to glow. Some of these creatures glow for protection, camouflage or to attract mates.

192 Join the Discussion

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  1. Hey Wonderopolis!
    I hope I am the first to comment today! Today’s Wonder was awesome, and the video was certainly cool! Once we had a glow-in-the-dark magnet that showed a lighthouse at night! I used to wonder about it but today I found the answer. I think tomorrow’s wonder would be about some really good mountain-climber who acts in a circus! I don’t know if that’s a rather silly idea, but I’ve read books in which people act in circuses and then climb anything so easily!


    • Welcome back, Laserdudle! We are glad you’re WONDERing with us today! We Wonder what you learned from today’s glow-in-the-dark Wonder? We’ve been thinking of those cool stars that you can stick to your ceiling and they glow at night! :)

  2. Hello, I am Jacob in Mrs. Ski’s class.

    I liked today’s wonder about glow in the dark things. I did not know that it is just simple science.

    • Hi there, Jacob B! We sure are glad you’re WONDERing with us today! Thanks for letting us know that you learned something new– science is AWESOME! :)

    • It’s cool that you had glow sticks for trick-or-treating, Blakeleigh! We think it’s interesting that your glow sticks are no longer working, too! We bet there’s a reason behind that– the chemicals in the glow sticks have released all their energy! :)

    • Great question, Jonathan! Today, we learned about different types of chemicals that can make things glow! Some chemicals must react with one another in order to produce a glowing light– by bending or snapping the glow stick, the reaction occurs! :)

  3. We are glad to be back and wondering! Some of us kept up with Wonderopolis (like Olivia) over our long break! How WONDERful is that?!?

    We thought that today’s wonder was interesting. Kaitlyn liked learning about the chemical reaction in glow sticks. We could all clearly imagine that familiar snap of the glow stick.

    Sam wonders why people say to put glow sticks in the freezer to make them work again.

    We think tomorrow’s wonder will be about a person who has climbed Mt. Everest, Spiderman, a famous mountain climber, a mountaineer or someone who helps people climb.

    • Welcome back to our Wonder Friends in Mrs. Ski’s AM Class! We were happy that some of our Wonder Friends stopped by over the holidays– it was WONDERful to say hello!

      We are so happy to hear that you’re WONDERing about chemicals that create a glowing effect! We believe the temperature in the freezer slows down the chemical process. This helps release less energy and light can be produced for a longer period of time!

      We can’t wait to climb up tomorrow’s Wonder with you! We’re so glad you’re back! :)

  4. We enjoyed today’s wonder, but we still had a few questions. Is the chemical in the glow sticks poisonous if we consume it and will it hurt our skin if we get it on us?

    We think tomorrow’s wonder is about the 2 men that made it to the top of Mt. Everest.

    • What a great question from our Wonder Friends in Mrs. Karr’s Class! While most of the chemicals are non-toxic, they could be harmful if they get in your eyes or are ingested. Your skin or eyes might be irritated if the chemicals touch you in any way, but they do not contain anything that will burn you. While glow sticks are fun to use, it’s important to use them safely! :)

      Thanks for reminding us about safety, Wonder Friends! We can’t wait to climb up tomorrow’s Wonder with you! :)

    • WOHOO, we think today’s Wonder is bright, too, Gabrianna! Thanks for sharing your guess with us, too! See you tomorrow! :)

  5. Hello I’m Payton from Mrs. White’s class and my computer isn’t working so I just saw a kid playing with glow sticks about 2 seconds long.

    • Hi there, Payton! We’re sorry that you can’t watch today’s Wonder video! Sometimes the computers and Internet in a school take some time to stream videos. We hope you’re enjoying today’s Wonder… perhaps you can watch the video a bit later? :)

  6. In the video clip, what were the children doing with the paper? Was it paper or something else?

    Also, why does tonic water make things glow. We would think that it should not be edible.

    Mrs. H’s 4th grade class

    • Hi there, Wonder Friends in Mrs. H’s Class! We did some research about today’s Wonder video, and the 3 and 4 year olds in the video were experimenting with light and mylar (a type of stretched film). You might be familiar with mylar balloons– they’re usually silver, shiny and filled with helium!

      We’re also glad you asked about tonic water. When you shine a black light on tonic water (or you’re in the dark), the phosphors in the beverage become excited– that’s what makes it glow! We have heard that tonic water can be good for you (it has been used to help leg cramps), but it also has an ingredient called quinine that probably is not the best for you. We think you make a good point, Wonder Friends! If it’s glowing, do you really want to drink it? :)

  7. We learned that glow sticks use chemiluminescence. We learned that bioluminescence comes from nature. We learned that bioluminescence is like jellyfish. We learned that radioluminescence is used to make a watch glow and uses radium. We learned that they put two chemicals in the glow sticks to make a phosphor. We liked that in the video, the way the girl made the star at the end.

    • WOW, we’re so proud of all the Tigers1stGrade/K! Some of the words in today’s Wonder are extra long… we’re so happy that you summarized what you learned today!

  8. Thank you Wonderopolis for such an “enlightening” wonder for today! Here’s what we thought:

    “It was nice to see how things light up. We used your wonders to draw some amazing things on the computer. We made light-up fish, glow fish, and fireflies!”

    • Hi there, PA Kindergarteners! Thanks for letting us know that you enjoyed today’s Wonder! We’re all lit up inside! :)

      It sounds like our Wonder Friends had a great time creating glow-in-the-dark creatures today! Hooray for WONDERing! :)

  9. We thought today’s wonder was glow-tastic (Kaden’s word) and made JK think of Christmas lights. We have all played with something that glows in the dark.

    We think tomorrow’s Wonder will be about the guy who climbed Mt. Everest, a mountain climber, a famous tight rope walker, King Kong, a goat, yodelers, or a sherpa.

    • We like that word, thanks Kaden! Today’s Wonder made us light up inside– and it helps that our Wonder Friends from Mrs. Ski’s PM Class are here, too! We can’t wait to find out what tomorrow’s Wonder will be… we’ve got our climbing gear ready! :)

    • Alright, that’s great news, Berkleigh! We Wonder if you have ever tried any glow-in-the-dark experiments? Or will you try one in the future?! :)

  10. I think that when things glow in the the dark it’s because someone who works for the glow company puts special chemicals in the glow sticks to make it glow in the dark… to me it sounds really cool and maybe someday I will work there.

    • Hey there, Mermaid girl! We think your idea for a glow in the dark company sounds cool! We Wonder if you learned about how some animals glow naturally, like jellyfish? :)

    • Hey there, Wonder Friend I! The beauty of the glow stick is that when you “break” it, the chemicals react to make things glow! How cool! :)

    • Great question from our Wonder Friends in Mr. Baumann’s class! We’re happy that you’re WONDERing with Mr. P. in the library! Two of the chemicals involved are luminol and hydrogen peroxide! Those react with one another and cause a magical glow! :)

    • We’re excited to see that Wonder Friends Alex, Sam and Cambria are WONDERing with us today! The chemicals, luminol and hydrogen peroxide, react with one another to create the glow! We’re so excited that you are WONDERing about things that glow today! :)

    • Hi there, Wonder Friends from Hopkins Elementary! We’re excited that Koko#12, Servine and Jordan are WONDERing with us today! It’s so much fun to Wonder about things that glow! Thanks for sharing your awesome comments, and ideas for new Wonders, too! :)

  11. I want to know what the chemicals are that are in glow sticks. I think our science teacher should teach us about glow sticks. It would be cool to make our own glow sticks.

    • Hi there, Wonder Friends Ally!, Makaylee, and Abby! Thanks for sharing your comments with us today! We learned that the chemical reaction causes the stick to glow, but it only lasts for so long. After the reaction is complete, the light dies down. The chemicals involved are luminol and hydrogen peroxide! :)

    • Great question, Levi B! The dark light allows us to see the chemical reaction light up! That’s what happens when a glow stick glows! :)

  12. Maybe the next wonder of the day should be: How do they make baseballs? But I like today’s wonder of the day! It’s cool to know how things glow in the dark.

    I love glow-sticks, there AWESOMEEEEE in fact I’m going to thow a party at night so that all the light is glow sticks thanks.

    <3-a student

    • Hey there, Wonder Friend A! We are so excited that today’s Wonder made you light up inside! We think your glow-in-the-dark party sounds like a blast, too! Thanks for sharing your comment with us! :)

    • Great question from Mrs. Brandon’s 2nd Grade class! WOHOO! Glow-in-the-dark candy includes some of the same elements that are found in glow sticks. You just need tonic water to create some food coloring that glows! :)

    • That’s right, Michaela! The liquid and the chemicals in a glow stick react and create a beautiful light– all through science! :)

    • It has to do with the light, TBoy#4! Under a black light, the white shirt appears to glow, thanks to the contrast between dark and light! :)

  14. I love wonderopolis!!!! Can you do a wonder about why nuclear explosions have more than one shockwave tomorrow? (11/28/12) Please I need to know!!!!! Thanks Wonderdude out.

    • Hi there, Wonderdude! We’re so excited that you enjoyed our Wonder today! It takes us some time to get our Wonders together– we’ve always got some research to do! However, we appreciate your comment and your idea to Wonder about explosions! :)

    • We’re glad you liked it, Anvita! The children in the Wonder video are having fun using glow-in-the-dark toys and mylar, a type of thin film! :)

  15. Hey Wonderopolis. I found today’s wonder of the colorful. And Michaela read this: Glowing in the dark — also known as luminescence — simply requires chemicals that store energy when exposed to light. These special substances are called phosphors. This type of glowing is sometimes called phosphorescence.
    Phosphors radiate visible light after being energized. This means you have to expose the items to light for a while before they will glow in the dark.
    Phosphors then slowly release their stored energy over time. As they release the energy, they emit small amounts of light, which we see as an object glowing. I think tomorrow’s wonder of the will be about hikers or mountian climbers.

    • Thanks for your WONDERful comment, Mushkale! We love when our Wonder Friends help one another out! We hope you’re having a SUPER day… great guess for tomorrow, too! :)

  16. Hi guys. How do things glow in the dark? I never knew it was simple science. I’m not afraid of the dark so now I need a flashlight.

    From Gurtej.

    • We’re glad you enjoyed today’s Wonder, Gurtej! The chemical reaction we’ve Wondered about today creates a glowing light. When the chemicals react they create light– it’s easy to see when you’re in the dark! :)

    • We can’t take credit for the Wonder video, Kultar, but it sure looks like fun! We LOVE WONDERing about new things with great friends like you! :)

  17. Oh and I think tomorrow’s wonder of the will be about Mount Everest or the first people who climbed Mount Everest. And Wonderoplis what’s your ALL-TIME favorite Wonder?

    • Thanks so much, Suhail! We are so glad you are enjoying your time at Wonderopolis! We are just two years old, as of this November! :)

  18. Hi Wonderopolis!!!

    I like the video of all the glow-in-the-dark things!

    The clue for tomorrow sounds exciting! I think that tomorrow’s wonder of the day is about “the first person in the world to climb a mountain and now he is a professional climber and could climb any mountain!!” I wonder if by “someone” it could be an animal? I wonder if my wonder will be right? Thanks for making this wonder, I like it!

    • WOHOO, we’re so glad you enjoyed today’s bright Wonder, Vickie! We can’t wait to find out what tomorrow’s Wonder will be… we hope to see you tomorrow! :)

  19. Hi guys hope you remember me from last year I love today’s wonder I never learned that but now how they work it was a mystery so sometimes I check wonderopolis this is what I did not know There are a couple of other types of luminescence. Chemiluminescence, for example, makes object glow in the dark because of a chemical reaction. When two particular chemicals react, they produce energy that is subsequently released, creating a glow. This is what happens in glow sticks. I think tomorrow’s wonder will be about Mount Everest. :)

    • Hey there, Wonder Friend Aidan! Welcome back ! We’re glad that you have learned some new information about glow sticks, Aidan! We hope to see you tomorrow! :)

  20. Hi my name is Kabir I wonder who were the first people who climbed the mountain for tomorrow’s wonder. Also I have a question do you guys choose the videos or is it automatic?

    • Hi there, Wonder Friend Kabir! We’re excited for tomorrow’s Wonder, too! We also like your question about our videos– we choose each and every one of them for our Wonder Friends to enjoy! :)

  21. You guys are the best I’m coming here for wonders will you do some thing about parasites because in school I’m writing about parasites for a feature article.

  22. Hey wonderopolis thanks for all of the great info on glow sticks. I also have two questions; the first one is how long can a glow in the dark toy stay active? And the second one is do jellyfish have all of the stuff glow sticks have because some types of jellyfish can glow in the dark right? Well thanks again and I can’t wait for the next wonderopolis bye :) :) :) !

    • Hey there, Tabby, you’ve got some great questions! We Wonder if you can find the answer for your first question in today’s Wonder article? Your second question, about jellyfish, is SUPER! Jellyfish use bioluminescence to glow– it’s something that happens in nature. We’ll see you tomorrow, Tabby! :)

  23. Wonderopolis I have been waiting over a week and I still didn’t get a reply!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    • Hi there, Wonder Friend Chase! We’re sorry to hear that you didn’t receive a response yet! We Wonder where you left your comment? We’d love to answer it!

  24. I have always wondered how stuff glows in the dark. I just got this glow bracelet at school and I was wondering why it was not glowing yet. My teacher says it needs to get light in order for it to glow.

    • How cool, Mark! We bet your glow-in-the-dark bracelet is SUPER cool! Thanks for sharing your comment with us– we hope you have a SUPER day! :)

    • Hey there, Jona! We Wonder if you checked out today’s Wonder! We learned about glow-in-the-dark chemical reactions that cause things to glow! :)

    • We bet there’s something out there like that already, Jordynn! Perhaps you’ll find some when you walk into a store that sells unique gifts! We’re glad you enjoyed today’s Wonder! :)

  25. Audrey was amazed to learn that animals have chemicals in their bodies.
    Ben wants to know if it is true that glow sticks have glass inside of it that breaks and two chemicals combine to make it glow?

    • Hi there, Wonder Friends in Mrs. Mastrullo’s Class! We’re so happy that you’re WONDERing about such bright things today! We agree with Audrey– it’s amazing to think about jellyfish that glow, and the chemicals that exist in all of our bodies! Ben has a great question, too! There are tiny glass capsules inside a glow stick– so very tiny that you can’t really see it. The chemicals react with one another when you bend or shake a glow stick– the capsules break and the chemicals can great a bright light! :)

  26. This was so cool! I have always wondered how things glowed but I never had the time to look it up! Thanks for sharing! Also, thanks for making wonderopolis possible. I am home schooled and this is always my favorite part of the day!

  27. Me and my friend cracked some glow sticks in half then we rubbed them on ourselves and turned off the lights and we started to glow!

    • YIKES, we sure hope you and your friend are okay, Naya B! We know it sounds like a cool idea, but we wouldn’t want you to have a skin reaction to the chemicals! Thanks for WONDERing with us today! :)

    • Hi there, Wonder Friend H! We’re sorry to hear that today’s video wasn’t one of your favorites, but we appreciate your comment! Perhaps we’ll see you soon! :)

  28. I loved this article, I used it for my homework assignment like Megan did too! My class does wonderopolis every Wednesday. I love wonderopolis!!!

    • WOHOO, we’re so happy to hear that you learned something new from Wonderopolis, Elizebath! We LOVE WONDERing with you and your classmates each Wednesday! :)

    • We’re not certain, Isaac! We bet it would be hard to see since all the mini capsules need to be contained in order to glow! :)

  29. Yes we’re okay we washed it all off as soon as we came back from bible school.But we’re (obviously) still alive today. But we just were WONDERing about what would happen (to see if we would glow). And our science experiment was successful! So no reason to worry,we didn’t even get any bumps/goosebumps on us.

  30. I know a trick to keeping it glowing for a very very long time you stick it in the freezer my friend told me this and it works I’ve tried it.

    • There are chemicals that react inside a glow stick, Noah! When they react, they create the glow that you see in the dark! :)

    • Hi there, Wonder Friends Qunicy, Krystal and Cameron! We’re glad you’re WONDERing about monsters… we appreciate your suggestion! :)

  31. I never knew there was another word for glow-in-the-dark like luminescence. I learned that phosphors radiate visible light after being energized. I might use these new vocabulary words in a science experiment. Why do glow-in-the-dark toys sometimes only glow for a short time? What wears down? I think tomorrow’s (12/7) wonder will be about a stone statue that looks like it is watching you.

    • Hi there, Wonder Friend John! We are excited that you’re WONDERing about things that glow and the chemical reactions that make that happen! Learning new vocabulary words is always WONDERful, too! We learned that chemical reactions take place, the “glow” occurs. However, that cannot go on forever– once the elements have reacted with one another, they glow and then slowly fade. You can put a glow stick or toy in the freezer, which helps slow down the chemical reaction, letting the light glow longer, too! :)

  32. Thanks for posting my video! I was intrigued as to why my views shot up by hundreds all of a sudden and then I found your site! Your website is a lovely place for resources, we will definitely be back to check out the Wonders of the Day! Glowsticks are awesome!

    • Hi there, Jessica! Thank you for sharing your video with us– we have SO many Wonder Friends who really enjoyed it! It was a perfect fit for WONDERing about things that glow in the dark! We hope you’re having a terrific day… and a WONDERful weekend! :)

    • Hi there, Angela! We are so glad you shared your glowing story with us! Thanks for providing more information about your book, too! :)

    • Hi there, Wonder Friend Atianna H! We’re glad you stopped by Wonderopolis today! Your school assignment sounds cool- we’re glad to be a part of it! We hope you have a fun time WONDERing! :)

    • There are LOTS of Wonder Friends here at Wonderopolis, Holly57584! We all take turns reading and responding to comments, and thinking up new Wonders of course! :)

  33. Oh my gosh!!!!!!
    This is an awesome website. I can find a lot of interesting facts about almost everything. Thank you to whoever created this website.

    • You can click directly on the video, Caroline! If you’re at school and it doesn’t work, you might want to try at home. We hope you can watch this Wonder video soon! :)

  34. I didn’t quite understand the video as much but what I have seen in the middle I thought was pretty interesting I actually am having fun WONDERing. :D

    • We’re so happy that you’re enjoying your time at Wonderopolis, A. Hart! We enjoyed watching the glowing video, too! It involves preschoolers and lots of different lights! :)

  35. Dear wonderopolis,
    I loved learning about how glow sticks glow in the dark! I loved the facts about how… glowing in the dark which is also known as luminescence simply requires chemicals that store energy when exposed to light. These substances are called phosphors.
    What do strontium aluminate, chemiluminescence, radioluminscence and bioluminescence mean?


    • We Wonder if you can do some research of your own to find out what those chemical-related words mean, Anna? Take a look at the Wonder and use the Internet to better understand those very long words! :)

    • Hi there, Michelle! We are glad you shared your comment with us- adding some glow in the dark elements to our clothes sounds like a great way to make us glow! :)

    • Thanks for sharing your comment with us, Coca Jesica! We hope you learned something new from our glowing Wonder, we sure did! See you soon, Wonder Friend! :)

    • That’s awesome news, Wonder Friend Noah! We’re so glad you visited us today to Wonder about cool things that glow in the dark! Here at Wonderopolis, we try to listen to all kinds of Wonders so we can share the awesome information with cool Wonder Friends like you! You can even nominate your Wonder here: If you have something that you’ve been WONDERing about, let us know! :)

    • Great question, Wonder Friend Matt! A chemical reaction takes place to make the glow sticks glow! For many glow sticks, bending or cracking them create the chemical reaction… and in turn, the stick will glow! :)

  36. How do you make glow sticks? Do you like glow sticks? When I was 3 years old, one day I got a glow stick and I was biting it and I was in the car.
    That video was awesome and cool! P.S. I am in Miss Barboza’s class

    • Hey there, Chato, thanks for visiting us today! We’re glad you enjoyed our gLoWiNg Wonder today! We think glow sticks are super cool, but we are glad to know you’re okay after biting one. There are chemicals inside that create the “glow”, but they’re not good for us to eat. Phew! :)

      We’re so glad you are here, Wonder Friend, and thanks for telling us that you’re in Miss Barboza’s class! A shout out to all our Wonder Friends in your classroom! :)

    • Hey Wonder Friend Madalyn! WAHOO! Summer break is SO exciting! What will you be WONDERing about this summer? We have LOTS of cool Wonders in store for the summer months! Talk to you again soon! :)

    • We agree, Chyra! We especially liked how the light of the glow sticks reflected off of the table! It looked cool! Thanks for WONDERing with us today! :)

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Have you ever wondered…

  • How do things glow in the dark?
  • What are phosphors?
  • Can you make your own glow-in-the-dark crafts?

Wonder Gallery

Glow in the DarkhhjellyfishVimeo Video

Try It Out

Ready to make your own homemade glow-in-the-dark crafts? Check out the cool variety of craft projects below and choose one or more to make with a friend or family member.

Be sure to check the list of supplies first. You may need to make a quick trip to the store to get a few things you’ll need.

When you’re finished, take a picture of your finished project and share it with your Wonder Friends on Facebook. We can’t wait to see what you make!

Still Wondering

National Geographic Xpeditions’ Bioluminescence lesson focuses on bioluminescence and features a cool photo gallery!

Wonder What’s Next?

Tomorrow’s Wonder of the Day is about someone who can climb any mountain!

Upload a Photo or Paste the URL of a YouTube or SchoolTube Video.