Last summer I spent a few days at RIT taking some seminars on engineering and what different courses would be like, one of the professors was demonstrating some of the materials we would get to use and he produced a an object consiting of two metal plates sandwiching some other sort of material with two wires leading out of it. He then demonstrated that if you apply heat to one side and a relativly colder object to the other, you could get a current running through the wires. He called this a solid state device because it had no moving parts inside. I understand that it is easy to get energy from an imbalance such as the temperature imbalance between the plates (I believe thats the 2nd law of thermodynamics). But if someone could explain the innerworkings of this device like how it turns the heat into electrical energy, or any other information on these devices, that would be most appreciated.