Conventional laser cavities contain huge numbers of atoms and photons, each contributing to the radiation field by stimulated emission. The effect of an individual photon on the dynamics of such a system is negligible. But if reduced to its bare essentials, a laser would become a pumped single atom that interacts with a single electromagnetic mode in a cavity. In so minimal a system, quantum fluctuations on the scale of single photons can become dominant and the usually familiar behavior of a laser can become very unfamiliar.