Grab some toothpicks, a bag of marshmallows, and our free printable shape cards for a fun, hands-on geometry and engineering activity! Kids will love building 2D and 3D shapes while learning about structure, balance, and geometry through play.
Marshmallow Shapes STEM Activity
Field of Science: Geometry, Engineering
Grade Level: Preschool – Middle School
Concepts Explored:
- Identifying and constructing 2D and 3D shapes
- Understanding vertices, edges, and faces
- Exploring stability and balance in structures
- Practicing fine motor skills and spatial awareness
Supplies Needed
- Mini marshmallows (or gumdrops)
- Toothpicks
- Printable Marshmallow Toothpick Shape Cards (free below)
- Flat surface for building
- Optional: Laminator for reusable cards
👉 Download the Free Printable Marshmallow Toothpick Shape Cards to guide kids as they build both flat and 3D structures! Print and laminate for durability. Kids can match, trace, or build directly from each card.
How to Build Marshmallow Toothpick Shapes
- Set Up: Place marshmallows and toothpicks within easy reach.
- Pick a Card: Choose a shape from the printable deck—start simple, then try 3D.
- Connect: Use marshmallows as vertices (corners) and toothpicks as edges (sides).
- Test Stability: Gently press on your structure—does it stay standing or wobble?
- Expand: Combine shapes to make new creations like houses, bridges, or towers!
💡 STEM Tip: Encourage kids to redesign shapes that collapse to learn how structure and angles affect stability.
What Shapes Can Kids Build?
2D Marshmallow Shapes
Square:
A four-sided shape with equal-length sides and four right angles.
➡️ Build it: Connect four equal toothpicks at the corners using marshmallows.
Triangle:
A three-sided shape with three angles that add up to 180°.
➡️ Build it: Connect three toothpicks at each marshmallow corner.
Rectangle:
Four sides, opposite sides equal, with all right angles.
➡️ Build it: Use four toothpicks and four marshmallows.
Pentagon:
Five sides and five corners.
➡️ Build it: Connect five toothpicks in a loop with marshmallows at each vertex.
3D Marshmallow Shapes
Pyramid:
A base with triangular sides meeting at a single apex.
➡️ Build it: Make a square base, then connect corners to a top marshmallow.
Cube:
Six square faces and twelve equal edges.
➡️ Build it: Form two squares and connect corners with vertical toothpicks.
Rectangular Prism:
Six rectangular faces, opposite faces equal.
➡️ Build it: Use 12 toothpicks, connecting all corners with marshmallows.
Pentagonal Prism:
Two pentagon bases connected by five rectangles.
➡️ Build it: Make two pentagons, then connect their corners with toothpicks.
Differentiation by Age
Preschool (Ages 3–5)
- Focus on simple shapes like squares and triangles.
- Encourage exploration and play—count sides and corners out loud.
- Builds fine motor and shape recognition skills.
Elementary (Ages 6–11)
- Introduce 3D structures and talk about stability and balance.
- Work in teams to encourage communication and problem-solving.
Middle School (Ages 12–14)
- Add engineering challenges—build towers or bridges that hold small weights.
- Discuss load distribution and structural integrity.
More Geometric Shape Activities
More Building Challenges for Kids
- Marshmallow Catapult: Build and launch mini marshmallows!
- Building Bridges: Build a bridge that holds coins or small toys.
- Strong Paper Structures: Test which shapes hold the most weight.
- Straw Boat Challenge: Float your creation and test buoyancy.
- Marshmallow Spaghetti Tower Challenge: Build the tallest tower possible.
- Marshmallow Igloo STEM Project: Build a marshmallow igloo!
Printable Science Packs for Kids
Visit our SHOP for easy-to-print STEM and science lesson plans for the whole year. Or join us in the Little Bins Club.
