  New particles can manifest their effects in many settings, ranging from
effects on sub-atomic to galactic length scales. The nature of these effects
depends on the specific particles and their non-gravitational interactions. In
this chapter, we give a brief overview of how atomic, molecular and optical
systems can be used to search for new particles. To illustrate the basic
principles behind these methods, we focus on the simplest class of particles,
namely new spinless bosons.
