This is a simple illusion with a powerful explanation of the difference between belief and faith.  Pour a splash of water into a cup and suggest that you "believe" that this water will freeze in the cup allowing you to turn the cup upside down over your head without it falling out.  Some might say they believe it with you.  Since they might believe, even for the sake of going along, offer to pour it over their head first.  Should they agree, the water won't fall out of the cup therefore proving their belief was correct.  But more than that it is a powerful example of the simple difference between belief and faith.  Anyone can believe but faith requires "action."  Comes with full explanation and script and a generous amount of special powder that causes the water to gel.  Works perfectly in a standard styrofoam cup.