  In quantum optics, it is common to assume that atoms can be approximated as
point-like compared to the wavelength of the light they interact with. However,
recent advances in experiments with artificial atoms built from superconducting
circuits have shown that this assumption can be violated. Instead, these
artificial atoms can couple to an electromagnetic field at multiple points,
which are spaced wavelength distances apart. In this chapter, we present a
survey of such systems, which we call \textit{giant atoms}. The main novelty of
giant atoms is that the multiple coupling points give rise to interference
effects that are not present in quantum optics with ordinary, small atoms. We
discuss both theoretical and experimental results for single and multiple giant
atoms, and show how the interference effects can be used for interesting
applications. We also give an outlook for this emerging field of quantum
optics.
