Nikolas Zoller examines the working principles and the underlying theoretical foundations of a microscopic heat engine. In particular, he investigates the system's stochastic dynamics in the underdamped regime which has hardly been studied in the past, but will be experimentally feasible in the near future due to recent technological developments. Emphasis is put on the maximization of the engine's efficiency at maximum power through optimization of the driving protocol. In addition, possible experimental realizations of a microscopic heat engine are discussed.