I went to the Arizona State fair about two years ago and found this man selling these absolute gems, I believe I paid 7 or 8 dollars US for them each. They are a clear liquid sealed in a thick soft plastic and there is a "button" inside the liquid and when the button is "snapped" a chemical reaction happens and these crystals start to form in the clear liquid. It kinda looks like highly viscous salt water when the reaction is done and it is very plyable in your hand. Now let me tell you, this thing gets HOT, almost to the point to where it burns your skin to the touch (130 degrees Farenheit). It takes about an hour or so for it to cool down and then it hardens. The coolest thing about these things is that you can boil them for about 5 minutes and they return to liquid again! You can re-use it for hundreds of times! Get more info here: http://www.reheater.com You will love these things, I stuck two of them in my MAIN first aid / survival kit and I thought I would share the resource with you all.