This set of slides was presented at the CNLS Smart Grid Seminar Series at Los Alamos National Lab on April 6, 2010. It presents new methods to model and control the aggregated power demand from a population of thermostatically controlled loads. The control objective is to produce relatively short-time scale responses (hourly to sub-hourly) for ancillary services such as load following and regulation. The control signal is applied by manipulation of temperature set points. The methods leverage the existence of system diversity and use physically-based load models to inform the development of a new theoretical model that accurately predicts - even when the system is not in equilibrium - changes in load resulting from changes in thermostat temperature set points.