We give a simple introduction to the theoretical treatment of atoms interacting strongly with electromagnetic fields in the radiofrequency, microwave and laser domains. In particular, we discuss the concept of dressed atoms, which considers the combination of the atom and photons as a composite physical system. This powerful concept has a wide range of applications in atomic physics and we give a few examples of its use in the manipulation of ultracold atoms in adiabatic potentials. These examples are selected from experimental work conducted by our research team in Oxford but there are numerous other applications and we outline some future possibilities.