I'll pretend you don't mean "sustained" to allow me to type something. Does this qualify?
Put a bowl of water down at room temperature, wait for one molecule to "evaporate", and I think you did it? Unfortunately they are now no longer at the same temperature.
Temperature is an average. You can still take advantage of the fact that there will be much lower and higher temperatures present. Also, what about Peltier effect? Same temperature when it starts.