1 teaspoon of Borax, a 4 oz container of Elmer's school glue, one cup of warm water.
You'll also need a wide bowl and a spoon.
You can also add food coloring dye and glitter (and even buy special kits online that will help you make glow in the dark slime.). Some people online said the dyed slime can leave stains on hands and clothes. If that happens to you, vinegar can help with the stain removal.
Start by adding one teaspoon of Borax to your one cup of water. Make sure the borax dissolves into the water. I had to stir mine a little bit.
In your bowl, pour the entire container of school glue. If you're going to use dye, add it now to the glue. I purposefully left off the amount of dye because it's really based on how light or dark you want your slime to be. Stir in your drops of food coloring into the clue, until you've found a color you like.
When that's ready, pour in some of the water with dissolved borax. Then stir. Pay close attention to what's happening in the bowl. Keep stirring. You should see areas turning into globs of slime. Pour more of the water with dissolved borax in.
Keep stirring. Touch the mixture to see its texture and how things are turning out. You want to be patient here. The first time I made this, I got impatient, poured in the entire cup of water plus the undissolved Borax at the bottom, stirred it quickly, and made a substance closer to Silly Putty than slime.
When the slime is a texture you like, take it out of the bowl. Press on it, pull, roll it out. Doing this will let you (or the child you're helping do this experiment) see how a non-Newtonian fluid does change its shape based upon the amount of pressure you apply to it.
There are many other slime recipes out there using different materials. Shaving cream added in can make the slime fluffy. Instead of using Borax, you can use baking soda and contact lens solution (in the united states, most contact lens solutions have boric acid in them).
Want to learn some of the sciene behind this recipe? Go here.