STEM Tuesday– Tiny Worlds (Microscopic/Nanotech)- In the Classroom

This month’s STEM Tuesday theme revolves around the small, the tiny, and the microscopic—from nanotechnology to microorganisms. Microbes and fungus may be small, but their effects in the world are far from that. They are vital to Earth’s complex, constantly cycling systems, which range from microscopic to monumental. What could microbes do? Try this activity in the classroom to help students understand how microorganisms can have big effects.


Yeast + Sugar Balloon Experiment

Student Prep

Read through Tiny Creatures: The World of Microbes by Nicola Davies and It’s a Fungus Among Us: The Good, the Bad & the Downright Scary by Carla Billups and Dawn Cusick as a class. Then tell students that microbes are in everything from the soil to our bodies to even our food. Explain that they will be doing a microbial experiment using yeast (a microorganism that is a member of the fungi kingdom). Then distribute materials to groups of students.

Tiny Creatures: The World of Microbes by Nicola Davies

This book is perfect for the curious kid who wants to know how microbes work. All around the world—in the sea, in the soil, in the air, and in your body—there are living things so tiny that millions could fit on an ant’s antenna. They’re busy doing all sorts of things, from giving you a cold and making yogurt to eroding mountains and helping to make the air we breathe.

It’s a Fungus Among Us: The Good, the Bad & the Downright Scary by Carla Billups and Dawn Cusick

All about Fungus! Who wouldn’t want to read this book? In It’s a Fungus Among Us, you’ll meet the wild group of organisms that can turn ants into zombies and eat trillions of pounds of feces every day. They’re not all gross though, these are the same types of organisms that make cheese stretchy, add sour tastes to candy, and make bread rise!



  • empty clear water bottle
  • yeast packet
  • balloon (stretched out by inflating a few times)
  • warm water
  • 1 tsp. sugar


  1. Have students empty the yeast packet into the water bottle. Then tell them to pour some of the warm water inside. Students should move the bottle a bit to mix the yeast and water.
  2. Ask students to stretch the balloon over the water bottle opening and observe what happens in the next 5 minutes. They should record their observations.
  3. Next have students carefully remove the balloon. Tell them to add 1 tsp. sugar to the bottle and mix. Students can now put the balloon back over the bottle opening.
  4. Have students observe the mixture and the balloon over the next 20 minutes. They can record their observations ever 5 minutes.


As the yeast consumes the sugar in the warm water mixture, the microbes produce gas that inflates the balloon at the top of the bottle. Tell students that this process is called fermentation, which is a process used to make all kinds of foods that we eat. Bread becomes light and airy due to fermentation. Milk turns into yogurt or kefir because of fermentation. The fermentation process also helps humans and animals digest food. This is just one of the many examples of how microbes affect us on Earth.


Need more ideas for teaching middle-school students about microbes? Check out these resources:

  • BioEd Online, Science Teacher Resources from Baylor College of Medicine, Microbes
    This site has 12 lessons to help students investigate microbes related to health (bacteria, fungi, protists, and viruses). Students will learn that microbes have important roles in humans, and that some help while others cause diseases.
  • Microbiology Society, Microbe Passports
    Students can check out a virtual microscope on this site to study different microbes—from Bifidobacterium (which lives in human intestines) to Geobacter metallireducens (a metal-eating microbe that lives in muddy riverbeds).
  • Science News for Students, The dirt on soil
    Read all about the microbes in soil on this online science news publication site run by the Society for Science and the Public. It includes a glossary of “Power Words,” links for further reading, and a downloadable wordfind worksheet.


Karen Latchana Kenney loves to write books about animals, and looks for them wherever she goes—from leafcutter ants trailing through the Amazon rain forest in Guyana, where she was born, to puffins in cliff-side burrows on the Irish island of Skellig Michael. She especially enjoys creating books about nature, biodiversity, conservation, and groundbreaking scientific discoveries—but also writes about civil rights, astronomy, historical moments, and many other topics. Her award-winning and star-reviewed books have been named a YALSA Quick Pick for Reluctant Readers, a 2015 Book of Note from the TriState Review Committee, a 2011 Editor’s Choice for School Library Connection, and Junior Library Guild selections. She lives in Minneapolis with her husband and son, and bikes, hikes, and gazes at the night sky in northern Minnesota any moment she can.

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