To grow borax crystals    

Borax

Cups

String

Stick

Pipecleaners

Food colouring

You will want to set up your cups in a location where they won’t be disturbed. You will want to keep the Cubs from shaking, moving, or stirring the mixture once you have filled the cups.

Take a pipe cleaner and wind it tightly into a nest shape. Other shapes are possible too. To make it bigger, cut another pipe cleaner in half and wind it into the nest. Make one per cup.
Tie a short piece of string to the pipe cleaner nest, and then tie the other end of the line to a stick. The pipe cleaner nest should hang down about an inch.

Bring 4 cups of water to a boil and stir in the Borax until it is dissolved. There should be a little bit of Borax on the bottom of the pan or container that does not dissolve.

This lets you know you have added enough borax to the water, and it has become a supersaturated solution.
Pour ¾ cup of the mixture into each cup and add food coloring to the cups if desired. You do not have to add food coloring to the cups since the pipe cleaners are colored, but it can make crystals look a little bolder.

Put one of the pipe cleaner nests into each cup and lay the skewer across the top of the cups so they hang freely.

Try to make sure the pipe cleaners don’t touch the sides or bottom of the cups. If they do end up touching, the crystals will attach the pipe cleaner to the cup. They may break off when you try to pull it free.
Leave your geode shaped pipe cleaners in the borax solution overnight (or even two nights) until lots of crystals have grown on them!
Remove your borax crystals from the water and let dry on a layer of paper towels. Once dry, you can cut the fishing line off and you have a gorgeous crystal for your Cubs to observe!