Sublimation is a direct change from the solid state into the gas state while skipping over the change into the liquid state. A common example is dry ice changing into carbon dioxide vapor, or the process of freeze drying the water out of foods. In this video, iodine is heated until it changes directly into a violet gas and then can be seen changing back directly into it's solid crystal form. As with any chemical change or reaction, proper care should be observed. In this case, iodine was heated by an exhaust hood to vent away any fumes during this demonstration.