A clear film layer filled with air.
Who knew such a simple concept would be emotionally gratifying for a little human. We as parents, could be made to do this for hours at a time if it were possible. Fortunately, we would pass out only after thirty minutes. Mr Derek has always loved bubbles (we have one of those bubble machines that claim to produce gazillions of bubbles). So, every Spring when bubble concoctions are prevalent in the stores we pounce. Several dollars for weeks of fun. Duh. That is a no-brainer.