  Since the pioneering work of L\"uscher in the 1980s it is well known that
considering quantum systems in finite volume, specifically, finite periodic
boxes, can be used as a powerful computational tool to extract physical
observables. While this formalism has been worked out in great detail in the
two-body sector, much effort is currently being invested into deriving
analogous relations for systems with more constituents. This work is relevant
not only for nuclear physics, where lattice methods are now able to calculate
few- and many-nucleon states, but also for other fields such as simulations of
cold atoms. This article discusses recent progress regarding the extraction of
few-body bound-state and resonance properties from finite-volume calculations
of systems with an arbitrary number of constituents.
