  Bismuth telluride heat pump. 
This is a small bismuth telluride thermoelectric heat pump.  Apply a DC voltage and one side gets cold while the other side gets hot.  If you attach a good heat sink and fan to the hot side, you can pump heat out of something, cooling it down.  This particular device was deployed inside a USB-powered mini-fridge designed to cool one can of soda using power from your computer. 
Source: eBay seller goods_keeper 
Contributor: Theodore Gray 
Acquired: 28 March, 2009 
Text Updated: 29 March, 2009 
Price: $6 
Size: 1.5" 
Purity: <20%
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