Secret Message Shapes

Make 3-dimensional objects out of 2-dimensional shapes…and use them to send secret messages!

  • Target Age: 8-11
  • Learning Goals: Geometry; Science & Engineering
  • Related Episode: Episode 113: Eureeka

Goal: To recognize that 3-dimensional objects can be made from simple, 2-dimensional shapes.

Time: 25-30 minutes

Space: Desk or table


  • heavy-weight paper (24 lb. – 110 lb., available at office supply stores)
  • scissors
  • gluestick
  • markers
  • empty cardboard boxes (cereal, snack foods, etc.)
  • "Mystery Object" handout (pdf)


  • Print several copies of the "Mystery Object" handout on cardstock.
  • Set up a work space for your child that includes "Mystery Object" handouts, scissors, gluestick and markers.
  • Separate the glued seams of the cardboard boxes so they lie flat (for demonstration).
  • Put together two Mystery Objects (for demonstration).
  • Optional: Preview the episode or clip, and if using them with your child, cue up the videos via the links above


  1. Have your child look at the flattened boxes. Ask:What 2-dimensional shapes do you see? (Answers will vary with different boxes.) How do the 2-dimensional shapes make a 3-dimensional object? Encourage your child to fold the flat shapes back into boxes.
  2. Ask:What’s the difference between 2-dimensional and 3-dimensional objects? Where else do we see 2-dimensional shapes being used to make 3-dimensional objects? (Blueprints for structures, schematics for assembling household items, and some gift and storage boxes.)
  3. Optional: Use the episode or clip to further explore this idea.
  4. Tell your child that she is going to make her own 3-dimensional object out of a 2-dimensional shape, and use it to send a secret message! Show her the two irregular pyramids you made ahead of time. Demonstrate different ways they can fit together, face to face. Say that you've figured out a way to write a secret message that can be read only when three or four of the objects are put together just right. But first, she has to make her own!
  5. Have your child look at her "Mystery Object" handout. Ask:What 2-dimensional shapes do you see? (Triangles, square.) What do you think the 3-dimensional object will look like?
  6. Have her cut out and begin assembling her pyramid. Help with the cutting and folding as needed. After the object is made, Ask:Does your object look the way you thought it would?
  7. Challenge your child. Say:You can put three of these irregular pyramids together to make a cube, or four together to make a regular pyramid. Or you can make something else by putting them face to face. Once you have made something new with three or four of these, I'll show you how to write your secret message.
  8. After a few minutes, demonstrate how to write with markers across the objects so the message can be read only when all the pieces are put together.
  9. When she’s written her message, your child should swap the disassembled objects with you to see if you can reassemble them and read her secret message!

Take it Further

Share this activity’s Science, Technology, Engineering, Math (STEM) connections and invite your child’s comments:

Chemists draw 2-dimensional pictures of molecules to show how they string together in the 3-dimensional world. In medicine, doctors use 2-dimensional x-rays to better understand our 3-dimensional bodies. Structural engineers use plans and blueprints that are 2-dimensional versions of 3-dimensional structures. Industrial engineers design packaging that starts out as flat shapes that can be assembled into 3-dimensional containers.

Talk About It

Ask:Was there something you learned today that you didn't know before, or that you would like to try on your own?

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