This activity is part of the Germ Problem-Solvers: Using Engineering to Develop Solutions unit.

  1. Connect students’ responses about what they think makes people sick to real microbes through a See, Think, Wonder thinking routine.
  • Review students’ responses to the read-aloud discussion questions, “Why do you think Little Louie was sick?” and “How did Louie get sick?” that were recorded during the previous activity, Feeling Yucky. Ask if students have any additional ideas to add to the existing hypotheses.
  • Next, write down the names of common infectious illnesses on the board (“stomach bug”; common cold, flu, strep throat; etc.). Elicit students’ ideas about what they think causes these illnesses, building on their previous responses about what makes us sick.
  • Show students images of the viruses and bacteria responsible for these illnesses with the Introducing Microbes and Germs Image Gallery. Explain the following key ideas:
    • Germs belong to a group of tiny living things called microbes.
    • There are many kinds of microbes, and not all of them make us sick— some even help us! For example, show students a picture of intestinal bacteria (i.e. Lactobacillus, Bifidobacteria) from the Introducing Microbes and Germs Image Gallery and explain that we have microbes inside of us that help us digest food and absorb nutrients (these good gut microbes are also called probiotics).
    • Microbes that make us sick are called germs. Sometimes microbes can help protect us from germs by serving as a barrier. For example, we have microbes on our skin that help protect us from germs (an example of a good skin microbe is Vitreoscilla bacteria that can help reduce water loss and could aid with eczema; an example of bad skin germs includes the antibiotic-resistant Staphylococcus aureus which can cause staph infections such as a boil). Another example of microbes that help protect us from germs includes the good microbes in our mouths (i.e. Lactobacillus) that help fight off bad breath-causing bacteria and gingivitis (i.e. Bacteroides spp.).
  • As you show students the images of microbes and germs, use the See, Think, Wonder thinking routine as explained in resource, See, Think, Wonder, by Project Zero. Ask:
    • What do you see?
    • What do you think about that?
    • What does it make you wonder?
  • Students may recognize familiar images of microbes they have seen on signage, on the news, or online. However, many images may be new. Use students’ observations and questions to inform how you introduce the ideas about where germs are found in the next step.


  1. Help students make connections between the driving question, the unit challenge, and students’ experiences with germs.
  • Remind students of the unit driving question: How can we design a way to stop germs from spreading?
  • Remind students that in this unit, they will be working in small groups to design a solution to keep themselves and others healthy by stopping the spread of germs, so considering where the most “bad” germs are will help us find helpful solutions. You might say, “We can’t see individual germs with our naked eyes, but we can find out where they are by growing samples of the germs so there are enough of them to see without a microscope. You will watch a video of an investigation today to better understand where bad germs live so we can help stop the spread of germs.
    • Ask students if they think they have germs in their classroom. Where could they be hiding? What do they look like if enough of them grow together?
    • Build on students’ responses to elicit their ideas about where the most germ-filled place in the classroom or school might be. 


  1. Show a video and lead a discussion to help students determine where germs are found in their classroom or school.
  • Show students the video Growing Bacteria (2:11) by Sick Science! so they can see one way to visualize germs. Pause before the results are shown (at 1:28 into the video).
    • Ask students to brainstorm where they would want to collect germs from inside their classroom or school if they were going to do this investigation. Collect student responses on the whiteboard or chart paper. (Student responses may include: keyboards or tablet surfaces, desks, pencils, doorknobs, railings, library books, playground equipment, water fountains, skin, hair, pets, etc).
    • Show the rest of the video to share the results of the investigation.
    • Ask students which surfaces in their classroom might be similar to a TV remote, cell phone, or soap dispenser, in terms of the presence of germs. (Possible responses: Students might say that a hand sanitizer pump might be as highly used as a soap dispenser, or that a light switch, hall pass, or doorknob might be as high-touch as a TV remote, or that their laptops or other digital devices might be similar to a cell phone).
    • Lead students to the idea that surfaces that are often touched by people tend to have high numbers of germs, both good and bad.
    • Have students make a prediction about the most high-touch places in their classroom or school. Record students’ responses on the chalkboard or whiteboard.
    • Ask students to note the difference in the number of germs growing in the samples that were not disinfected as opposed to the samples that were disinfected (at 1:33 into the video). Prompt students to make the connection that using disinfectants on surfaces is one way to help slow the spread of germs in our environment. Note for students that we still need good germs to help our bodies and the environment, so it’s important to consider other ways to avoid illness caused by bad germs while not killing off all of the germs in an area—like maintaining a balanced diet (i.e. consuming naturally-derived probiotics) to sustain a positive gut microbiome environment that can fight off infections caused by bad germs.
    • Please note: the EPA (United States Environmental Protection Agency) recommends that kids not use disinfectants, including wipes, as these kind of products typically contain a label that says "keep out of reach of children.” This is mostly out of concern that they would use them incorrectly and use them on their skin rather than surfaces. Educators may show the correct procedure for disinfecting surfaces, and explain why students shouldn't do it themselves yet. 
    • Let students know that in the next activity, Invisible Villains, they will learn more ways to slow the spread of germs.


Informal Assessment

Discussion: In class discussions, students will show their ability to participate in collaborative conversations about germs in small and larger groups to make connections, ask questions, and track the cause and effect of germs growing in high-touch places.

Extending the Learning

Build on the ideas in this activity by reading an age-appropriate text that introduces the different types and distinctions between microbes and germs. One option is the book Tiny: The Invisible World of Microbes by Nicola Davies (7:25).

Subjects & Disciplines

  • Biology
    • Health
  • Engineering

Teaching Approach

  • Project-based learning

Teaching Methods

  • Brainstorming
  • Demonstrations
  • Discussions

Skills Summary

This activity targets the following skills:

Connections to National Standards, Principles, and Practices

Common Core State Standards for English Language Arts & Literacy

Next Generation Science Standards

What You’ll Need

Required Technology

  • Internet Access: Optional
  • Tech Setup: 1 computer per classroom, Projector

Physical Space

  • Classroom


Throughout this unit, students will be working in project teams (small groups of three or four) as they design a solution to a germ-related problem. Some work that students do will be submitted individually, but they will collaborate to create group solutions and present those solutions as a group.


  • Large-group instruction
  • Small-group work

Background Information

Microbes are organisms that are too small to be seen by the naked human eye and include bacteria, archaea, protists, viruses, and fungi. Although some microbes cause disease, they are also crucial to the functioning of human bodies through processes such as digestion and strengthening of the immune system (collectively called the “human microbiome”), and terrestrial and aquatic ecosystems on Earth through processes such as nutrient and energy cycling.


In the video, the microbes that are growing in the petri dishes are fungi or bacteria and not necessarily the microbes that make students sick. The video is a model to help students think about where germs are found in their classroom environment and can help students identify specific problems as they connect to the project.

Prior Knowledge

  • None

Recommended Prior Activities



gelatinous extract of red algae used especially for growing cultures


disease-producing microbe.

petri dish

small, shallow dish made of glass or plastic with a loose cover used for growing bacteria cultures


forecast or projected outcome of a situation.