To comprehend why bubbles exist, your kids would need to know some substantial principles of physics and chemistry--electrons, hydrogen bonding, surface tension. But to blow a stream of beautiful bubbles, they need only a casual knowledge of soap science. A delightful way to introduce the subject is with a homemade bubble factory.

Begin by mixing up a batch of bubble soap. In a clean 1-gallon jug, combine 12 cups of cold water with 1 cup of liquid dish-washing soap (Joy and Dawn work best) and 1 tablespoon of glycerine (also known as glycerol; it's available at drugstores). For a crash course in bubble science, explain to your children that a bubble is a thin film of liquid surrounding a pocket of air. Water is not flexible enough to hold the air, so soap is added to make the water more elastic (the surface doesn't burst when air is forced inside it). To prove this, have your kids try blowing bubbles with water, then let them experiment with the solution.

Next, challenge your kids to create bubbles of all sizes. For mini versions, have them dip plastic straws into the solution and gently blow. The soap scientists can use just one straw or, for connected bubbles, tape half a dozen together and blow through them all at once. A wand for small, individual bubbles can be made by bending a short length of wire (a large paper clip works fine) into a lollipop shape with a 1-inch diameter loop and wrapping the handle with duct tape. For larger spheres, bend a hanger into a circle with a short handle and wrap pipe cleaners around the loop. This enables the wand to hold more solution (to avoid creating froth, try not to swirl the wand in the solution too much).

To measure their lung capacity, have your kids take a deep breath and slowly blow through a straw on the surface of a pan of solution, pulling the straw up as they blow (the stronger their lungs, the larger the bubble will be).

Finally, challenge them to make frozen bubbles by blowing a few on a plate and slipping them into a freezer.