Various models of physics beyond the Standard Model predict the existence of ultralight bosons. These particles can be produced through superradiant instabilities, which create boson clouds around rotating black holes, forming so-called "gravitational atoms". In this talk, I discuss the interaction between a gravitational atom and a binary companion, in two distinct scenarios. In the case of a compact binary detected through gravitational waves (GWs), the cloud undergoes "resonances" and "ionization", which leave a characteristic mark on the emitted GWs. When the gravitational atom is at the center of a nuclear star cluster, such as the Sgr A* cluster, it induces a measurable precession of the stellar orbits, and drives some of them to decay into the supermassive black hole in a few Myr.