When your child is learning shapes, the triangle is pretty easy to identify — three corners, three sides. But the ho-hum triangle gets a whole lot more intriguing when you tell her it's one of the strongest shapes on earth. Because each of its angles is fixed, it won't change shape or size when pressure is applied to the points. You can prove it by going 3-D.

What you'll need:

How to make it:

1. Make a triangle base from three small, thin pretzel sticks and three large gumdrops, flat sides down. (It helps to poke holes in the gumdrops before inserting the pretzels.) 
2. Add on three more triangle sides, joined at the top by a single gumdrop, flat side down — you've formed what's called a tetrahedron.
3. To test the structure's strength, build four tetrahedra and arrange them in a square formation. 
4. Now balance a book on top. Add another book, and another. How many can it hold? ]When you're done, your child can eat the architecture, of course.
5. Keep the geometry lesson going by looking for triangles outside the house — on the playground, say. Or check out the Spaceship Earth pavilion — a geodesic dome at Walt Disney World's Epcot. The dome's basic structural unit? Triangles.

Originally published in Wondertime magazine.