Gather Ingredients

You'll need only three ingredients to make this sweet, extremely viscous green goo come to life:

1 3/4 cups tonic water
1/3 cup potato starch
2 tablespoons lime-flavored gelatin dessert powder (such as Jell-O)

Cook

Combine all the ingredients in a medium saucepan over medium heat, then stir constantly until the mixture is thick and goopy, about 2-3 minutes. Let the mixture cool.

Play

That's it! Once your slime is cool, it's ready to go. (And it's best used right away, so there's no need to wait.) Wet your hands before picking it up to help prevent it from being too sticky. You can even cover the slime with about a half-inch of water to make handling easier. 

Drape the slime over a cup, serve it on a cupcake, feature it in the centerpiece of your Halloween spread — just use your imagination and have fun. Discard the slime after you are done playing. And the next time an urge to make glow-in-the-dark slime strikes, change up the color by simply using a different flavor of powdered gelatin.