  The elements of micromaser physics are reviewed in a tutorial way. The
emphasis is on the basic theoretical concepts, not on technical details or
experimental subtleties. After a brief treatment of the atom-photon interaction
according to the Jaynes-Cummings model, the master equation that governs the
dynamics of the one-atom maser is derived. Then the more important properties
of the steady states of the one-atom maser are discussed, including the trapped
states. The approximations, upon which the standard theoretical model of the
one-atom maser is based, are exhibited. The methods by which one calculates
statistical properties of the emerging atoms are hinted at.
