Thank you Martha Stewart Halloween special! I saw this and just had to try it. Fill bottom of container with 1 to 2 inches of water. Add food coloring until desired color is reached. Tilt bottle slightly, and carefully pour vegetable oil into container, creating a layer on top of water, filling to about 1 to 2 inches below the opening of the container. Break Alka-Seltzer tablets in half and drop into container as desired. They will sink directly through the oil layer and begin bubbling in the water layer, drawing the colored water up through the oil like a lava lamp! It is so AWESOME!