Marshmallow Geometry STEM Challenge

Ready for a fun STEM challenge that uses stuff you already have in your house, that also teaches engineering and math skills? Check out this Marshmallow STEM Building Challenge!


Geometry STEM Building Project

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Kids love to create and build, especially when it involves using sweet treats! In this activity we used simple materials we had around the house, but there are so many different variations you can do based on your own supplies. The most important thing is for kids to have fun, get creative, and to sneak in some learning!

STEM Building Challenge

For this challenge we will be learning some geometry (math) and engineering (building). You can do this challenge with kids as young as preschool, but even my middle school aged kid benefited from this lesson. And really? Even adults can have fun creating!

3D Hexagon Design Project

I will walk you through how to do a 3D Hexagon design but you can tackle any design you like.

For this project you will need:

  • Marshmallows (small ones work great)
  • Toothpicks

That’s it! See, so simple!

If you are using larger marshmallows, or even something like gummies, play dough, or other candies, you may want to switch out for something stronger like skewers or even crafting sticks. I’ll share more ideas on that in a moment.

Want to make your own marshmallows? It is actually a great kitchen science project with our Marshmallow Making Project for Kids.


In this project we are learning some important math skills. Specifically you will want to explain to your kids these terms:

The marshmallows are the vertices.

Toothpicks are the edges.

Then you have the faces of the shapes.

The shape we are building first is a hexagon. Hexa means six in Greek. A hexagon is six sided polygon. It must have 6 edges and 6 vertices.

3D Hexagon Build Project

Now it’s time to build a 3D Hexagon!

  1. Build the Base

    Start by building your base. Like any building project the base is the supporting structure and the most important part of building a stable project.

    For the base we need to create a hexagon shape around the outside. We will need 6 edges (toothpicks) and 6 vertices (marshmallows) for this.Hexagon Geometry Lesson

  2. Stablize the Base

    To add strength we need to add supporting structures through the centre of our Hexagon base. Guess what? We need 6 edges for this step too! Place a tooth pick in each marshmallow pointing towards the centre of the hexagon. Attach a marshmallow in the centre to create the central vertices.

  3. Prep the Edges and Vertices

    Once you have your base created it is time to start going up! Your kids might find it easier to add a marshmallow onto each toothpick before they start going up. Marshmallow STEM Build

  4. Going Up

    Place two tooth picks in each marshmallow pointing up and out (use one of your pre-attached ones with a marshmallow on the end). Now add a toothpick across attaching the two edges. Repeat around the structure.

  5. Adding Stability

    Now we need to add some more internal strength. So we are going to add another Hexagon through the middle that duplicates the base design. Place a tooth pick in each marshmallow pointing towards the centre of the hexagon. Attach a marshmallow in the centre to create the vertices.Hexagon STEM Build

  6. Going Up Again!

    Now we need to add another level using the triangles design we used in step 4 again.

  7. Top layer

    For the final layer, create another hexagon to finish the top off with lots of strength and stability.

    Tip! Take a look at all of our pictures if you find any of these steps confusing. Once you start,it will make complete sense and is a fun and easy build!

  8. Hexagons everywhere!

    Now take a look at your creation. There are hexagons at each level, but you also have hexagons around the outside!Hexagon STEM Build

STEM Project Extensions

Looking at your hexagon design explore some of these ideas with them.

  • Are all the edges the same length?
  • As them how many edges/vertices/faces there are in the structure.
  • How many triangles can they find?
  • What type of triangle are they?
  • For more advanced students, have them work out the internal angle of a hexagon. Do this by taking the base layer and removing the internal a pieces. Now measure the interior angle at each vertices (Tip – Each interior angle is 120 degrees, so the total internal angle of any simple hexagon is 720 degrees).
  • Why not challenge the kids to see how tall they can build their structure and still keep it stable?
  • Or test your structure to see how much weight it can hold. Then see what you can do structurally to make it stronger.

Or why not have a Marshmallow STEM Build Minute To Win It Challenge like we did here.

Need a quick and easy educational challenge that kids will love, has a super quick clean up, and uses easy to find items? This Marshmallow Engineering Challenge is a fantastic engineering minute to win it type challenge that helps kids build their problem solving skills and can be adapted for a variety of levels.

Now you have explored Hexagons, what other 3D structures can you build and explore?

If you use different materials like candies or play dough, compare how well they worked and which ones were most effective. Tip – We found marshmallows best because they are so light and easy to work with but your preferences may be different.

For children still mastering literacy skills such as reading and spelling, this STEM Shapes Building Challenge is perfect.

On a teal blue wood slate background sits Scrabble letter tiles spelling out the word SHAPES. Above it sits a triangle shape made out of craft sticks and yellow play dough. Overlay Text says Shapes and Spelling STEM Challenge

Continue the learning with some fun printables that encourage kids to sort and graph shapes. These printables are available free of charge to all STEAM Powered Family members. Join now and get instant access to these printables, plus you will get regular emails from us with new educational activities, resources and printables.

This project was so simple but had some incredible learning moments, even for my teenager!

Have a great time exploring geometry and STEM with this hands on project!

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