Fill your bowl about halfway with water. (It's a good idea to do this in a sink or another area that can afford to get a little messy!)
If you have food coloring to add to your oobleck, now's the best time to add it—we added about 2 drops of yellow and 3 drops of blue to ours. Food coloring can be pretty messy, so make sure you to have an adult's help for this step.
Gradually add cornstarch to the water, stirring with the spoon, until the mixture is a little bit thicker than cake batter. You can continue to experiment with the thickness of your oobleck later on in the experiment.
Oobleck is a non-Newtonian fluid, which means that it shares properties of both liquids and solids. Try hitting the surface of your oobleck with the palm of your hand. Now, try resting your hand on the surface. What happened?