A mixture of corn starch
. It can behave as a liquid
, depending on how much force
you apply. Roll it around in your hands, and it forms a ball. Let it sit, and it melts into a puddle. Great fun.
To make it, start out with some corn starch and add water little by little, stirring constantly. Stop when the water and corn starch are completely mixed, but before it's too easy to stir. Add green food coloring for the complete experience.